Mary bought a total of 250 big and small sweets. Then she decided to exchange 60% of her big sweets for the small ones in the ratio of 3 : 7. After the exchange, she had 290 sweets. What percentage of the sweets she bought were small ones?
| |
Big sweets |
Small sweets |
Total |
| Before |
5 u |
? |
250 |
| Change |
- 3 u |
|
|
Comparing big and
small sweets at exchange |
- 3 u |
+ 7 u |
+ 40 |
| After |
2 u |
? |
290 |
60% =
60100 =
35The number of big sweets that were exchanged for small sweets was repeated.
Number of extra sweets that Mary received due to the exchange
= 7 u - 3 u
= 4 u
4 u = 290 - 250
4 u = 40
1 u = 40 ÷ 4 = 10
Number of small sweets at first
= 250 - 5 u
= 250 - 5 x 10
= 250 - 50
= 200
Percentage of the sweets Mary bought that were small ones
=
200250 x 100%
= 80%
Answer(s): 80%
