Here, a = 10% and b = 20%
According to the formula,
Required answer= [b ± a/(100 - b)] x 100 %

Correct Option: D

Here, a = 10% and b = 20%
According to the formula,
Required answer= [b ± a/(100 - b)] x 100 %
= (20 - 10)/(100 - 20 ) x 100%
= (10/80) x 100% = 12.5 % gain
+ ve sign show that profit is earned here.

Let the market weight = 1 kg = 1000 g
Real weight = 80% of 1000 = 800 g
Let the CP of 1 g = ₹ 1
∴ CP of 800 g = ₹ 800,
CP of 1000 g = ₹ 1000
SP = 120% of 1000 = (120/100) x 1000 = ₹ 1200

Correct Option: D

Let the market weight = 1 kg = 1000 g
Real weight = 80% of 1000 = 800 g
Let the CP of 1 g = ₹ 1
∴ CP of 800 g = ₹ 800,
CP of 1000 g = ₹ 1000
SP = 120% of 1000 = (120/100) x 1000 = ₹ 1200
Gain = 1200 - 800 = ₹ 400
∴ Gain % = (400/800) x 100% = 50%

Given that, a = 10% and b = 30%
According to the formula,
Required per cent = [(b - a)/(100 - b)] x 100

Correct Option: D

Given that, a = 10% and b = 30%
According to the formula,
Required per cent = [(b - a)/(100 - b)] x 100
= [(30 - 10)/(100 - 30)] x 100
= (20/70) x 100 = 200/7%
= 28⁴/₇% profit

According to the formula,
Gain% = [Error / (True value - Error)] x 100%
= [80/(100 - 80)] x 100%

Correct Option: B

According to the formula,
Gain% = [Error / (True value - Error)] x 100%
= [80/(100 - 80)] x 100%
= (80/920) x 100%
= 8¹⁶/₂₃ %

Given that, a = 4%, b = 28 g and c = 32 g
Required profit = [(100 - a) x (c/b) -100] %
=[(100 - 4) x (32/28) - 100] %
= [96 x (32/28) - 100]%

Correct Option: A

Given that, a = 4%, b = 28 g and c = 32 g
Required profit = [(100 - a) x (c/b) -100] %
=[(100 - 4) x (32/28) - 100] %
= [96 x (32/28) - 100]%
= [(96 x 8)/7 - 100]%
= (768 - 700)/7 %
= 68/7 %
= 9⁵/₇ % gain
+ ve sign shows that profit is earned here.