+197 Faisal used 1/3 of his money to buy 5 erasers and 11 pencils. Each eraser cost 3 times as much as a pencil. He then bought more erasers with 3/4 of his remaining money.
(a) What fraction of his money was left?
(b) How many erasers did he buy altogether?
+128473 (a) Let M be the total money that he started with
What he had left after buying the 5 erasers and 11 pencils = M - (1/3)M = 2/3 M
(b) This is a little more difficult
Since each eraser cost 3 times as much as a pencil let the cost of a pencil = P and the cost of an eraser = 3P
So he spends 5 * 3P = 15P on erasers and 11P on pencils
So the erasers represent 15 / ( 15 + 11) = (15/26) of the the (1/3)M = (15/26) (1/3)M = (15/ 78)M = the cost of 5 erasers
So each eraser cost ( 15/78)M / 5 = (15/ 390) M = (5/130)M = (1/26)M
He spends (3/4) of his remaining money on some more erasers so he spends
(3/4) (2/3)M = (1/2)M on erasers
So the number of additional erasers that he buys = (1/2)M / (1/26)M = 26/ 2 = 13
So, in total, he buys 5 + 13 = 18 erasers
