PSLE Mark and Archie have the same total number of coins. Mark has a number of fifty-cent coins and 41 twenty-cent coins. The total mass of his coins is 0.45 kg. Archie has a number of fifty-cent coins and 61 twenty-cent coins.
- Who has less money in coins? How much less? Give your answers in this format. (Eg Adam, $12)
- Each fifty-cent coin is 1.5 g heavier than each twenty-cent coin. What is the total mass of Archie's coins in kg?
(a)
Both boys have the same number of coins. Since Archie has more twenty-cent coins than Mark, it means that Archie has less fifty-cent coins than Mark. So Archie has less money.
Difference in the number of twenty-cent coins.
= 61 - 41
= 20
Difference in the value of 1 twenty-cent coin and 1 fifty-cent coin
= 50 - 20
= 30¢
Amount that Archie had less than Mark
= 20 x 30
= 600¢
= $6
(b)
Difference in the mass between 20 twenty-cent coins and 20 fifty-cent coins
= 20 x 1.5
= 30 g
= 0.03 kg
Total mass of Archie's coins
= 0.45 - 0.03
= 0.42 kg
Answer(s): (a) Mark, $6; (b) 0.42 kg