Mary was saving money to buy pens. She saved $6 every 7 days. After saving for 49 days, she went to buy pens that were on sale.
- What was the most number of pens she could buy?
- Mary wanted to buy 36 pens. How much more did she need to save?
(a)
Number of sets of 7 days
= 49 ÷ 7
= 7
Amount that Mary saved in 49 days
= 7 x 6
= $42
Maximum number of sets of 8 pens that Mary could buy
= 42 ÷ 11
= 3 r $9
Remaining amount left after buying sets of 8 pens = $9
Maximum number of sets of 4 pens that Mary could buy with $9
= 9 ÷ 6
= 1 r $3
Remaining amount left after buying sets of 4 pens = $3
Maximum number of pens that Mary could buy with $3
= 3 ÷ 3
= 1
Most number of pens that Mary could buy
= 3 x 8 + 1 x 4 + 1
= 24 + 4 + 1
= 29
(b)
Number of sets of 8 pens that Mary could buy
= 36 ÷ 8
= 4 r 4
Number of sets of 4 pens that Mary could buy
= 4 ÷ 4
= 1 r 0
Amount that Mary needed to buy 36 pens
= 4 x 11 + 1 x 6
= 44 + 6
= $50
Amount that Mary needed to save more
= 50 - 42
= $8
Answer(s): (a) 29; (b) $8
