Given that, a = 20 and b = 15
According to the formula,
Profit %= [(a - b) / b] x 100 %

Correct Option: B

Given that, a = 20 and b = 15
According to the formula,
Profit %= [(a - b) / b] x 100 %
= (5/15) x 100% = 100/3 %
= 33¹/₃%

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.

Let required percentage profit = N%
According to the question,
10% of (80 x 50) = 5% of (20 x 50) + N% of (60 x 50)

Correct Option: C

Let required percentage profit = N%
According to the question,
10% of (80 x 50) = 5% of (20 x 50) + N% of (60 x 50)
⇒ (80 x 50 x 10)/100 = [(20 x 50 x 5)/100] + (60 x 50 x N)/100
⇒ 80 = 10 + 6N
⇒ N = 70/6 = 11²/₃%

Required loss = (a/10)² %

Correct Option: A

Required loss = (a/10)²%
= (20/10)²% = 4%
Thus, seller gets 4% loss in the deal.