Risa bought some presents for her colleagues at an average price of $11.70. If Risa decided to buy a pen which cost $19 for her father and a bag which cost $34 for her mother, the average price of the presents would become $15.40. How many presents did Risa buy for her colleagues?
| |
Colleagues |
Colleagues and parents |
| Number |
1 u |
1 u + 2 |
| Value |
11.70 |
15.40 |
| Total Value |
11.70 u |
15.40 u + 30.80 |
Number of presents that Risa bought for her colleagues = 1 u
Amount that Risa spent on the presents for her colleagues
= 1 u x 11.70
= 11.70 u
Amount that $(Lizy) spent if she bought for her parents
= 19 + 34
= $53
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
= 15.40(1 u + 2)
= 15.40 u + 30.80
11.7 u + 53 = 15.40 u + 30.80
15.40 u - 11.7 u = 53 - 30.80
3.7 u = 22.20
1 u = 22.20 ÷ 3.7 = 6
Number of presents that she bought for her colleagues
= 1 u
= 6
Answer(s): 6
