Remainders — answers

for a grown-up3 questions

This is the marking copy and it carries every answer. Her sheet is the other file — same numbering, same margin codes, so you can mark straight down the page.

  1. G21-A202 marks

    Shirley packed 163 lollipops into plastic bags of 7 lollipops. She used the most number of plastic bags possible. She sold each plastic bag of lollipops at $6 and each remaining lollipop at $2. How much did she get after selling all the lollipops?

    answer 142

    method Divide to find the bags: 163 ÷ 7 = 23 bags with 2 lollipops left over. The bags bring in 23 × $6 = $138, and the 2 loose lollipops bring in 2 × $2 = $4. Total = $138 + $4 = $142.

    watch Throwing away the remainder. The 2 left-over lollipops are still sold — at a different price, which is exactly why the remainder matters here.

  2. M26-B84 marks

    Joshua had more than 10 and fewer than 40 candies. When she packed the candies in bags of 7, she was left with 2 candies. When she packed them in bags of 3, she had no candies left. How many candies did Joshua have?

    answer 30

    method "Bags of 7 with 2 left over" means the number is 2 more than a multiple of 7: 7+2=9, 14+2=16, 21+2=23, 28+2=30, 35+2=37. Keeping only those between 10 and 40: 16, 23, 30, 37. "Bags of 3 with none left" means a multiple of 3, and of those four only 30 is. So Joshua had 30 candies.

    watch Listing the multiples of 7 themselves (14, 21, 28, 35) and forgetting to add the remainder of 2.

  3. D01-A22 marks

    What is the smallest number greater than 1 that leaves a remainder of 1 when it is divided by 2, by 3 and by 4?

    (A) 7   (B) 9   (C) 13   (D) 25   (E) 49

    answer (C) — 13

    method Take away the remainder: the number minus 1 must divide by 2, 3 and 4, so it is a multiple of 12. The smallest is 12, giving 13. (25 and 49 also work, but they are not the smallest.)