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Practice: growth and decay

Practice: growth and decay

1

Gal deposited 6,000 ₪ for five years, at 4% interest a year.

a

How much money will the deposit hold at the end, with simple interest?

    / – 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 much money will the deposit hold at the end, with compound interest? Round to agorot.

      / – 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

      By how many shekels does compound interest give more?

        / – 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 car was bought for 80,000 ₪.
        Its value falls by 12% every year.

        a

        What will the car be worth after three years?

          / – 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 percent of the price did the car lose in the three years? Round to two digits after the point.

            / – 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 friend says: “It lost 3⋅12%=36%\displaystyle {3\cdot12\%}={36\%}.” What is his mistake?

            3

            A loaf of bread costs 12 ₪ today.
            Inflation is 3% a year.

            a

            What will the loaf cost in ten years, if its price rises like all prices? Round to agorot.

              / – 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 will 5,000 ₪ kept at home be worth in ten years, in today’s prices? Round to agorot.

                / – 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

                Bank A offers a compound interest of 3% a year.
                Bank B offers a compound interest of 0.25% a month.

                a

                Work out the factor for a year in Bank B. Round to four digits after the point.

                  / – 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

                  Dor deposits 20,000 ₪ for five years in the bank that gives more. How much will he have at the end? Round to agorot.

                    / – 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

                    5

                    Noam has a credit card debt of 2,000 ₪.
                    The company charges a compound interest of 2% a month, and Noam pays nothing back.
                    After how many months will the debt pass 2,500 ₪? Work out the debt for two numbers of months that show the answer.

                    a

                    The debt after the first number of months:

                      / – 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 debt after the second number of months:

                        / – 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

                          / – 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

                          The graph shows the sum in a deposit at compound interest, x\displaystyle x years after it was opened.
                          The points A\displaystyle A and B\displaystyle B are on the graph.
                          Find the sum deposited and the interest rate, and write the function.

                          y= ?\displaystyle y=\,?
                          A=(0,5000)\displaystyle A=(0,5000)
                          B=(1,5400)\displaystyle B=(1,5400)