Percentage problems (grade 8)

Question

Dicky has some marbles in a bag. 40%of the marbles are blue and 80%of the remaining are red. There are 24 more red marbles than blue marbles.

(a) find the total number of marbles in the bag

(b)after he gives away some blue marbles, 10% of the remaking marbles are blue. Find the numbers of blue marbles left.

Answer 1

 There are 24 more red marbles than blue marbles.

So, if red is (.80)(.60) = .48, or 48%, and blue is .40 or 40%, then, .48 - .40 = .08, and that difference is equal to 24

.08x = 24

x = 300 marbles total

r = 144, b = 120, other = 36

after he gives away some blue marbles, 10% of the remaking marbles are blue. Find the numbers of blue marbles left

.10(300 - x) = b - x

.10(300 - x) = 120 - x

30 - .10x = 120 - x

.90x = 90

x = 100 number of blues given away

120 - 100 = 20 blues left