Question

Ravish bought 100 articles for rupees 4000 he sold 20 of them at a gain of 5% at what gain 5 percent.At what gain per cent must he sell the remaining article so as to gain 20% on the whole

Answer 1

$\huge\red{Answer\: is}$

CP of 100 article =Rs 4000

CP of 1 article = 4000/100
= Rs 40

Now
CP of 20 article = Rs 20 × 40
= 800
Gain = 5%
so
SP = CP(100+ GAIN% /100)
$= 800 \times \frac{(100 + 5)}{100} \\ = 8 \times 105 \\ = 840$
Total CP = 4000
Total Gain = 20%
Total SP =
$= 4000 \times (\frac{100 + 20}{100} ) \\ = 40 \times 120 \\ = 4800$
Now For Remaining Articles

CP FOR 80 ARTICLE = 80 × 40
= Rs 3200

SP FOR 80 ARTICLE = 4800 - 840
= Rs 3960

GAIN = SP - CP
= 3960 - 3200
= 760

GAIN % = GAIN × CP/100
$= \frac{760 \times 100}{3200} \\ = 23.75\%$
So He sell the remaining article at 23.75%
so as to gain 20% on the whole.

$<marquee>Hope it helps you$