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.

## Saturday, March 21, 2009

### Tao Nan School P5 SA2 2006 Math Q45

A box containing 58 iron balls weighed 2145g . when 46 of the iron balls were removed, the mass of the box and the remaining iron balls weighed 489g. What was the mass of the box?

Solution

Number of iron balls left when 46 were removed
58 – 46 = 12 (iron balls)

Box + 58 iron balls ----- 2145 g
Box + 12 iron balls ----- 489 g

(58 – 12) iron balls ----- 2145 g – 489 g
46 iron balls ----- 1656 g
1 iron ball ----- 1656 g divided by 46 = 36 g

Box + 58 iron balls ----- 2145 g
Box + (58 x 36 g) ----- 2145 g
Box + 2088 g ----- 2145 g
Box ----- 2145 g – 2088 g = 57 g

Answer: The box was 57 g.

Anonymous said...

12 is the number of balls remaining.

Excel Eduservice said...

Reworded statement. Thanks for pointing out.

Anonymous said...

Question on weight of 58 iron balls plus box should be 2145g. Your question wrote 2154.

Excel Eduservice said...

Amended. Thanks for highlight again.