m = marbles at first
e = erasers at first
m = 80
After he gave away 12 marbles he have 80 - 12 = 68 marbles,
After he gave away 25% of his erasers he have 75% erasers.
75% = 75 / 100 = 25 ∙ 3 / 25 ∙ 4 = 3 / 4
He have 68 marbles and 3 / 4 erasers.
He had a total of 128 marbles and erasers means:
68 + 3 / 4 e = 128
Subtract 68 to both sides
3 / 4 e = 60
Multiply both sides by 4
3 e = 240
e = 240 / 3 = 80
At first, Jareth 80 erasers.
25% = 25 / 100 = 25 ∙ 1 / 25 ∙ 4 = 1 / 4
Jareth give away 1 / 4 of 80 erasers.
1 / 4 ∙ 80 = 20
Jareth give away 20 erasers.
At first, Jareth had 80 marbles and some erasers. After he gave away 12 marbles and 25% of his erasers, he had a total of 128 marbles and erasers left. How many erasers did Jareth give away?
1 answer