Irene baked 50 shortbreads. 40% of them were strawberry shortbreads. How many more strawberry shortbreads must Irene bake so that 90% of her shortbreads are strawberry shortbreads?
| |
Strawberry shortbreads |
Other shortbreads |
| Before |
40% |
60% |
| Change |
+ ? |
No change |
| After |
90 u |
10 u |
Number of strawberry shortbreads at first
= 40% x 50
=
40100 x 50
= 20
Percentage of other shortbreads
= 100% - 40%
= 60%
Number of other shortbreads
= 60% x 50
=
60100 x 50
= 30
Number of other shortbreads in the end
= 100 u - 90 u
= 10 u
The number of other shortbreads remains unchanged.
60% = 10 u
10 u = 30
1 u = 30 ÷ 10 = 3
Number of strawberry shortbreads in the end
= 90 u
= 90 x 3
= 270
Additional number of strawberry shortbreads that Irene must bake
= 270 - 20
= 250
Answer(s): 250
