Let the initial quantity be n and the initial cost be c, so labour charges = 0.25c.... Total cost = c+0.25c=1.25c
The changed price = 1.15c and therefore, the labour price = 0.30*1.15c..... Total cost = 1.15c+0.3*1.15c=1.15c*(1+0.3)=1.15c*1.3 = 1.495 c or 1.5c
Let the changed quantity be r..

the total money spent has to be the same, so \(1.25c*n=1.5c*r.......\frac{r}{n}=\frac{1.25}{1.5}=\frac{125}{150}\)..
r as a % of n = \(\frac{125}{150}*100=\frac{250}{3}=83\)%

Thus reduction is 100-83=17%
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html
4) Base while finding % increase and % decrease : https://gmatclub.com/forum/percentage-increase-decrease-what-should-be-the-denominator-287528.html


GMAT Expert

chetan2u please see highlighted part it seems to be a typo error..
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