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- Standard 13
- Quantitative Aptitude
A trader purchase a wrist watch and a pendulum for $Rs.$ $390.$ He sells them making a profit of $10 \%$ on the watch and $15 \%$ on the pendulum. He earns a profit of $Rs$. $51.50 .$ The difference between the original prices of the pendulum and the watch is equal to? (in $Rs.$)
$80$
$120$
$110$
$100$
Solution
Let $CP$ of wrist watch be $Rs.\, x$
Then $CP$ of pendulum $=$ $Rs.$ $(390-x)$
$SP$ of wrist watch $=\frac{110 x}{100}=\frac{11 x}{10}$ $Rs.$
$SP$ of pendulum $=\frac{115}{100}(390-x)$
$=\frac{23}{20}(390-x)=448.5-\frac{23}{20} x$
Total $SP =\frac{11 x }{10}+448.5-\frac{23}{20} x =\frac{8970- x }{20}$
Total $C P=R s .390$
Net profit $=$ Total $SP$ $-$ Total $CP$
$51.50=\frac{8970-x}{20}-390$
$1030=8970-x-7800 \Rightarrow x=140$
So, price of wrist watch $=$ $Rs. 140$
price of pendulum $=$ $Rs. 250$
difference between original prices
$=$ Rs. $(250-140)=$ $Rs. 110$
