Topics in arithmetic (Chapter 10) 2176
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Activity Simple interest calculator#endboxedheading
Click on the icon to obtain a simple interest calculator.
What to do:
Use the software to check the answers toExamples 5to 10.In many situations we are given the final amount after a percentage has been added or subtracted. For
example, when Sofia was given a20%bonus, her total pay wasE 800. To solve such problems we need to
work in reverse. We let a variable represent the original amount, then construct an equation which relates it
to the final amount.Example 11 Self Tutor
Colleen receives5%commission on the items she sells. In one week she earnsE 140
commission. Find the value of the items she sold.Let the value of the items sold beEx.
We know that5%ofExisE 140 ,so 5%£x= 140
) 0 : 05 £x= 140
) x= 2800So, the value of the items sold wasE 2800.Example 12 Self Tutor
The value of an old book has increased by35%to$540. What was its original value?Let the original value be$x.
The value has increased by35%to$540, so we know that135%of$xis$540.) 135%£x= 540
) 1 : 35 £x= 540
) x= 400So, the original value of the book was$400:D REVERSE PERCENTAGE PROBLEMS [1.8]
SIMPLE INTERESTHow long would it take to earn interest of:
a $3000on a loan of$10 000at a rate of8%p.a. simple interest
b U82 440on a loan ofU229 000at a rate of6%p.a. simple interest?If you deposited$8000in an investment account that paid a rate of 7 :25%p.a. simple interest, how
long would it take to earn$1600in interest?IGCSE01
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Y:\HAESE\IGCSE01\IG01_10\217IGCSE01_10.CDR Wednesday, 24 September 2008 4:48:56 PM PETER