Betty was saving money to buy pens. She saved $8 every 7 days. After saving for 42 days, she went to buy pens that were on sale.
- What was the most number of pens she could buy?
- Betty wanted to buy 46 pens. How much more did she need to save?
(a)
Number of sets of 7 days
= 42 ÷ 7
= 6
Amount that Betty saved in 42 days
= 6 x 8
= $48
Maximum number of sets of 7 pens that Betty could buy
= 48 ÷ 10
= 4 r $8
Remaining amount left after buying sets of 7 pens = $8
Maximum number of sets of 4 pens that Betty could buy with $8
= 8 ÷ 6
= 1 r $2
Remaining amount left after buying sets of 4 pens = $2
Maximum number of pens that Betty could buy with $2
= 2 ÷ 2
= 1
Most number of pens that Betty could buy
= 4 x 7 + 1 x 4 + 1
= 28 + 4 + 1
= 33
(b)
Number of sets of 7 pens that Betty could buy
= 46 ÷ 7
= 6 r 4
Number of sets of 4 pens that Betty could buy
= 4 ÷ 4
= 1 r 0
Amount that Betty needed to buy 46 pens
= 6 x 10 + 1 x 6
= 60 + 6
= $66
Amount that Betty needed to save more
= 66 - 48
= $18
Answer(s): (a) 33; (b) $18
