Pamela baked 150 cookies. 30% of them were butter cookies. How many more butter cookies must Pamela bake so that 85% of her cookies are butter cookies?
| |
Butter cookies |
Other cookies |
| Before |
30% |
70% |
| Change |
+ ? |
No change |
| After |
85 u |
15 u |
Number of butter cookies at first
= 30% x 150
=
30100 x 150
= 45
Percentage of other cookies
= 100% - 30%
= 70%
Number of other cookies
= 70% x 150
=
70100 x 150
= 105
Number of other cookies in the end
= 100 u - 85 u
= 15 u
The number of other cookies remains unchanged.
70% = 15 u
15 u = 105
1 u = 105 ÷ 15 = 7
Number of butter cookies in the end
= 85 u
= 85 x 7
= 595
Additional number of butter cookies that Pamela must bake
= 595 - 45
= 550
Answer(s): 550
