Sarah baked 80 puffs. 25% of them were strawberry puffs. How many more strawberry puffs must Sarah bake so that 90% of her puffs are strawberry puffs?
| |
Strawberry puffs |
Other puffs |
| Before |
25% |
75% |
| Change |
+ ? |
No change |
| After |
90 u |
10 u |
Number of strawberry puffs at first
= 25% x 80
=
25100 x 80
= 20
Percentage of other puffs
= 100% - 25%
= 75%
Number of other puffs
= 75% x 80
=
75100 x 80
= 60
Number of other puffs in the end
= 100 u - 90 u
= 10 u
The number of other puffs remains unchanged.
75% = 10 u
10 u = 60
1 u = 60 ÷ 10 = 6
Number of strawberry puffs in the end
= 90 u
= 90 x 6
= 540
Additional number of strawberry puffs that Sarah must bake
= 540 - 20
= 520
Answer(s): 520
