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Review: finance and economics, grade 12

Review: finance and economics, grade 12

1

A bike-hire shop charges 40 ₪ a day, and hires out 60 bikes a day.
For every 2 ₪ rise in the price the shop hires out 2 bikes fewer.
x\displaystyle x is the number of rises, and the revenue a day is R=(40+2x)(60−2x)=−4x2+40x+2400\displaystyle {R}={(40+2x)(60-2x)}={-4x^{2}+40x+2400}.
Mark the parabola’s vertex on the graph.

y=−4x2+40x+2400\displaystyle y=-4x^{2}+40x+2400

a

Which price a day gives the shop the greatest revenue?

    / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

    / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

    b

    What is the greatest revenue a day?

      / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

      / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

      2

      A carpentry shop sells lamps at x\displaystyle x shekels a lamp, and sells 120−2x\displaystyle 120-2x lamps a month.
      Each lamp costs the shop 20 ₪, and its fixed costs are 600 ₪ a month.
      The profit a month is P=(x−20)(120−2x)−600\displaystyle {P}={(x-20)(120-2x)-600}.

      a

      Expand the brackets and write the profit in standard form.

        / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

        / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

        b

        At which price is the profit greatest?

          / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

          / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

          c

          Solve the equation: at which prices does the shop make neither a profit nor a loss?
          At which prices does it make a profit?

            3

            A bakery bakes cakes (x\displaystyle x) and pies (y\displaystyle y) for Friday’s sale.
            A cake takes an hour in the oven, and a pie two hours; the oven has 30 free hours.
            A cake needs 3 kg of flour, and a pie 2 kg; the bakery has 54 kg of flour.
            The profit on a cake is 30 ₪, and on a pie 40 ₪.

            a

            Write the constraints and the objective function.

            b

            On the graph, the lines of the two constraints: x+2y=30\displaystyle {x+2y}={30}, that is y=15−0.5x\displaystyle {y}={15-0.5x}, and 3x+2y=54\displaystyle {3x+2y}={54}, that is y=27−1.5x\displaystyle {y}={27-1.5x} (the dashed one).
            Mark the corner points of the feasible region, apart from the origin.

            y=15−0.5x\displaystyle y=15-0.5x
            y=27−1.5x\displaystyle y=27-1.5x

            c

            Solve the system of equations: where do the two lines meet?

              d

              Work out the profit at each corner point.
              How many cakes and how many pies should the bakery bake, and what is the profit?

              Cakes

                / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                Pies

                  / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                  / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                  The profit

                    / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                    / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                    4

                    On the town map a unit is 100 m.
                    Branch A\displaystyle A of a chain of corner shops is at the point (0,2)\displaystyle (0,2), and branch B\displaystyle B at the point (8,8)\displaystyle (8,8).

                    a

                    What is the straight-line distance between the branches, in map units?
                    And how many metres is that?

                      / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                      / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                      b

                      The chain wants to build a warehouse exactly halfway between the branches.
                      At which point?

                      c

                      A straight street runs between the branches.
                      On the graph board, write the street’s equation, and the equation of the street parallel to it through the petrol station C\displaystyle C.

                      A=(0,2)\displaystyle A=(0,2)
                      B=(8,8)\displaystyle B=(8,8)
                      C=(4,0)\displaystyle C=(4,0)

                      d

                      An avenue whose equation is y=−x+23\displaystyle {y}={-x+23} crosses the street between the branches.
                      Solve the system of equations: where is the junction?

                        5

                        A factory has 600 workers.
                        The monthly salary is normally distributed: the mean is 8000 ₪, and the standard deviation 1200 ₪.

                        44005600680080009200104001160034%34%13.5%13.5%2.5%2.5%Monthly salary (₪)
                        a

                        What percent of the workers earn between 6800 ₪ and 10,400 ₪?

                          / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                          / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                          b

                          How many workers earn more than 10,400 ₪?

                            / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                            / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                            c

                            What is the standard score of a worker who earns 9800 ₪?

                              / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                              / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                              d

                              The factory gives a grant to the 16% of the workers with the lowest salaries.
                              Up to which salary is the grant given?

                                / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                                6

                                A machine fills one-kilogram bags of sugar.
                                The weight is normally distributed: the mean is 1000 grams, and the standard deviation 5 grams.
                                A bag whose weight is more than two standard deviations from the mean leaves the production line.

                                a

                                Between which weights does a bag stay on the line?

                                Lower limit

                                  / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                  / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                                  Upper limit

                                    / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                    / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                                    b

                                    About how many bags out of 4000 leave the line?

                                      / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                      / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power

                                      c

                                      A bag weighs 1012 grams.
                                      What is its standard score?
                                      Does it leave the line?

                                        / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power

                                        / – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power