Olivia baked 100 shortbreads. 40% of them were butter shortbreads. How many more butter shortbreads must Olivia bake so that 90% of her shortbreads are butter shortbreads?
| |
Butter shortbreads |
Other shortbreads |
| Before |
40% |
60% |
| Change |
+ ? |
No change |
| After |
90 u |
10 u |
Number of butter shortbreads at first
= 40% x 100
=
40100 x 100
= 40
Percentage of other shortbreads
= 100% - 40%
= 60%
Number of other shortbreads
= 60% x 100
=
60100 x 100
= 60
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 = 60
1 u = 60 ÷ 10 = 6
Number of butter shortbreads in the end
= 90 u
= 90 x 6
= 540
Additional number of butter shortbreads that Olivia must bake
= 540 - 40
= 500
Answer(s): 500
