Betty was saving money to buy pens. She saved $6 every 7 days. After saving for 63 days, she went to buy pens that were on sale.
- What was the most number of pens she could buy?
- Betty wanted to buy 39 pens. How much more did she need to save?
(a)
Number of sets of 7 days
= 63 ÷ 7
= 9
Amount that Betty saved in 63 days
= 9 x 6
= $54
Maximum number of sets of 6 pens that Betty could buy
= 54 ÷ 11
= 4 r $10
Remaining amount left after buying sets of 6 pens = $10
Maximum number of sets of 3 pens that Betty could buy with $10
= 10 ÷ 7
= 1 r $3
Remaining amount left after buying sets of 3 pens = $3
Maximum number of pens that Betty could buy with $3
= 3 ÷ 3
= 1
Most number of pens that Betty could buy
= 4 x 6 + 1 x 3 + 1
= 24 + 3 + 1
= 28
(b)
Number of sets of 6 pens that Betty could buy
= 39 ÷ 6
= 6 r 3
Number of sets of 3 pens that Betty could buy
= 3 ÷ 3
= 1 r 0
Amount that Betty needed to buy 39 pens
= 6 x 11 + 1 x 7
= 66 + 7
= $73
Amount that Betty needed to save more
= 73 - 54
= $19
Answer(s): (a) 28; (b) $19
