PSLE Luis and Harry have the same total number of coins. Luis has a number of twenty-cent coins and 70 ten-cent coins. The total mass of his coins is 0.77 kg. Harry has a number of twenty-cent coins and 130 ten-cent coins.
- Who has less money in coins? How much less? Give your answers in this format. (Eg Adam, $12)
- Each twenty-cent coin is 2.2 g heavier than each ten-cent coin. What is the total mass of Harry's coins in kg?
(a)
Both boys have the same number of coins. Since Harry has more ten-cent coins than Luis, it means that Harry has less twenty-cent coins than Luis. So Harry has less money.
Difference in the number of ten-cent coins.
= 130 - 70
= 60
Difference in the value of 1 ten-cent coin and 1 twenty-cent coin
= 20 - 10
= 10¢
Amount that Harry had less than Luis
= 60 x 10
= 600¢
= $6
(b)
Difference in the mass between 60 ten-cent coins and 60 twenty-cent coins
= 60 x 2.2
= 132 g
= 0.132 kg
Total mass of Harry's coins
= 0.77 - 0.132
= 0.638 kg
Answer(s): (a) Luis, $6; (b) 0.638 kg