PSLE
Oscar and Tommy have the same total number of coins. Oscar has a number of twenty-cent coins and 43 ten-cent coins. The total mass of his coins is 0.899 kg. Tommy has a number of twenty-cent coins and 63 ten-cent coins.

1. Who has more money in coins? How much more? Give your answers in this format. (Eg Adam, $12)
2. Each twenty-cent coin is 2.5 g heavier than each ten-cent coin. What is the total mass of Tommy's coins in kg?

(a)
Since Oscar has less ten-cent coins than Tommy but both had the same number of coins, Oscar had more money.

Both boys have the same number of coins. Since Oscar has less ten-cent coins than Tommy, it means that Oscar has more twenty-cent coins than Tommy. So Oscar has more money.

Difference in the number of ten-cent coins.
= 63 - 43
= 20

Difference in the value of 1 ten-cent coin and 1 twenty-cent coin
= 20 - 10
= 10¢

Amount that Oscar had more than Tommy
= 20 x 10
= 200¢
= $2

(b)
Difference in the mass between 20 ten-cent coins and 20 twenty-cent coins
= 20 x 2.5
= 50 g
= 0.05 kg

Total mass of Tommy's coins
= 0.899 - 0.05
= 0.849 kg

Answer(s): (a) Oscar, $2; (b) 0.849 kg