This blog is managed by Song Hock Chye, author of Improve Your Thinking Skills in Maths (P1-P3 series), which is published and distributed by EPH.

## Sunday, April 24, 2011

### ACS Primary 2010 SA1 Math Paper 2 Q15

Both Joanne and Joseph had an equal amount of money at first. Every month, Joanne spent \$850 and Joseph spent \$912. After a few months, Joanne was left with \$1550 while Joseph had 4/5 as much as Joanne. How much money did Joseph have at first?

Solution

Every month,
Joanne spends \$850
Joseph spends \$912
Difference every month
--> \$912 - \$850 = \$62

After a few months, Joseph had 4/5 as much as Joanne,

5 units ----- \$1550
1 unit ------ \$1550 divided by 5 = \$310
(\$310 is the difference between Joanne and Joseph after a certain number of months)

Number of months to achieve the \$310 difference,
\$310 divided by \$62 = 5 (mths)
It also takes 5 months for Joseph to have 4/5 as much as Joanne.

Amount Joseph has at first,
Joseph ------ 4 units + (5 mths x \$912 spent per mth)
----- (4 x \$310) + (5 x \$912)
= \$1240 + \$4560
= \$5800