Let the two rates be R₁ and R₂

According to the question,
[(1000 x 2 x R₁)/100] - [(1000 x 2 x R₂)/100] = 20

Correct Option: C

Let the two rates be R₁ and R₂

According to the question,
[(1000 x 2 x R₁)/100] - [(1000 x 2 x R₂)/100] = 20
⇒ [2000 x (R₁ - R₂)] / 100 = 20
∴ R₁ - R₂ = 20/20 = 1%

Let rate is R%
According to the question.
[(R x 400 x 2)/100] + [(R x 100 x 4)/100] = 60

Correct Option: A

Let rate is R%
According to the question.
[(R x 400 x 2)/100] + [(R x 100 x 4)/100] = 60
⇒ 12R = 60
∴ R = 60/12 = 5%

Let entire sum = P
According to the question,
[(2P/3) x 3%] + [(P/6) x 6%] + [1 - ( 2/3 + 1/6 )] P x 12% = 25

Correct Option: A

Let entire sum = P
According to the question,
[(2P/3) x 3%] + [(P/6) x 6%] + [1 - ( 2/3 + 1/6 )] P x 12% = 25
⇒ [(2P/3) x (3/100)] + [(P/6) x (6/100)] + [1 - 4 + 1/6] x (12P/100) = 25
⇒ 2P/100 + P/100 + 2P/100 = 25
⇒ 5P = 2500,
∴ P = 500

Given, R₁ = 6% R₂ = 10%
According to the question,
800 + [(800 x 6 x T)/100] = 600 + [(600 x 10 x T)/100]

Correct Option: D

Given, R₁ = 6% R₂ = 10%
According to the question,
800 + [(800 x 6 x T)/100] = 600 + [(600 x 10 x T)/100]
800 + 48T = 600 + 60T
⇒ 12T = 200
⇒ 3T = 50
∴ T = 50/3 = 16²/₃ yr

Given, T₁ = 5 yr, R₁ = 10% and
T₂ = 10 yr, R₂ = 8%
Let the first part = P
Then, second part = (1521 - P)

Now, according to the question.
[(P x 5 x 10)/100] = [{(1521 - P) x 10 x 8}/100]

Correct Option: D

Given, T₁ = 5 yr, R₁ = 10% and
T₂ = 10 yr, R₂ = 8%
Let the first part = P
Then, second part = (1521 - P)

Now, according to the question.
[(P x 5 x 10)/100] = [{(1521 - P) x 10 x 8}/100]
⇒ 5P = 12168 - 8P
⇒ 13P = 12168
⇒ P = ₹ 936

So second part = 1521 - 936 = ₹ 585