PSLE
Tommy and Justin have the same total number of coins. Tommy has a number of ten-cent coins and 49 five-cent coins. The total mass of his coins is 0.774 kg. Justin has a number of ten-cent coins and 89 five-cent coins.

1. Who has less money in coins? How much less? Give your answers in this format. (Eg Adam, $12)
2. Each ten-cent coin is 2.8 g heavier than each five-cent coin. What is the total mass of Justin's coins in kg?

(a)
Both boys have the same number of coins. Since Justin has more five-cent coins than Tommy, it means that Justin has less ten-cent coins than Tommy.  So Justin has less money.

Difference in the number of five-cent coins.
= 89 - 49
= 40

Difference in the value of 1 five-cent coin and 1 ten-cent coin
= 10 - 5
= 5¢

Amount that Justin had less than Tommy
= 40 x 5
= 200¢
= $2

(b)
Difference in the mass between 40 five-cent coins and 40 ten-cent coins
= 40 x 2.8
= 112 g
= 0.112 kg

Total mass of Justin's coins
= 0.774 - 0.112
= 0.662 kg

Answer(s): (a) Tommy, $2; (b) 0.662 kg