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.

## Tuesday, December 11, 2007

### Anglo-Chinese School (Primary) P5 SA2 2006 Math Question (Q37)

The ratio of the number of 20-cent coins to the number of 50-cent coins to the number of \$1 coins in a bag is 2 : 4 : 7. Given that the total amount of money in the bag is \$47, how many coins are there altogether?

Solution

47 units ----- \$47 (Total amount of money in bag is \$47)

1 unit ----- \$47 divided by 47 = \$1

Value of 20-cent coins ----- 2 units ----- \$2
Value of 50-cent coins ----- 10 units ----- \$10
Value of \$1 coins ----- 35 units ----- \$35

No. of 20-cent coins ----- \$2 divided by 20 cents ----- 10 coins
No. of 50-cent coins ----- \$10 divided by 50 cents ----- 20 coins
No. of \$1 coins ----- \$35 divided by \$1 ----- 35 coins

Total number of coins in bag

10 + 20 + 35 = 65

Answer: There were 65 coins in the bag.

Anonymous said...

isn't it faster to do this:

Ratio 20 cents: 50 cents : \$1
= 2 : 4 : 7
2 x 20 cents + 4 x 50 cents + 7X 100 cents = 940 cents

4700 / 940 = 5 groups

5 x (2 + 4 + 7) = 65 coins

Excel Eduservice said...

Dear Anonymous,

My reply can be found here.