Erika bought some presents for her colleagues at an average price of $13.80. If Erika decided to buy a pen which cost $17 for her father and a bag which cost $33 for her mother, the average price of the presents would become $15.20. How many presents did Erika buy for her colleagues?
| |
Colleagues |
Colleagues and parents |
| Number |
1 u |
1 u + 2 |
| Value |
13.80 |
15.20 |
| Total Value |
13.80 u |
15.20 u + 30.40 |
Number of presents that Erika bought for her colleagues = 1 u
Amount that Erika spent on the presents for her colleagues
= 1 u x 13.80
= 13.80 u
Amount that $(Lizy) spent if she bought for her parents
= 17 + 33
= $50
Total number of items bought if she bought for her parents and her colleagues
= 1 u + 1 + 1
= 1 u + 2
Total amount that she spent if she bought for her parents and her colleagues
= 15.20(1 u + 2)
= 15.20 u + 30.40
13.8 u + 50 = 15.20 u + 30.40
15.20 u - 13.8 u = 50 - 30.40
1.4 u = 19.60
1 u = 19.60 ÷ 1.4 = 14
Number of presents that she bought for her colleagues
= 1 u
= 14
Answer(s): 14
