PSLE
Mark and Bobby have the same total number of coins. Mark has a number of ten-cent coins and 48 five-cent coins. The total mass of his coins is 1.246 kg. Bobby has a number of ten-cent coins and 68 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 2.1 g heavier than each five-cent coin. What is the total mass of Bobby's coins in kg?

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

Difference in the number of five-cent coins.
= 68 - 48
= 20

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

Amount that Bobby had less than Mark
= 20 x 5
= 100¢
= $1

(b)
Difference in the mass between 20 five-cent coins and 20 ten-cent coins
= 20 x 2.1
= 42 g
= 0.042 kg

Total mass of Bobby's coins
= 1.246 - 0.042
= 1.204 kg

Answer(s): (a) Mark, $1; (b) 1.204 kg