Required compound ratio = (2 x 5 x 4) / (7 x 3 x 7)

Correct Option: B

Required compound ratio = (2 x 5 x 4) / (7 x 3 x 7)
= 40/147
= 40 : 147

Given that
A : B = 3 4 = ( 3 x 2 ) : (4 x 2 ) = 6 : 8
B : C = 8 : 9

Correct Option: D

Given that
A : B = 3 : 4 = ( 3 x 2 ) : (4 x 2 ) = 6 : 8
B : C = 8 : 9
∴ A : B : C = 6 : 8 : 9
As consequent of the first ratio is equal to the antecedent of second ratio.

(a + b) / (a - b) = 5/3
⇒ 3a + 3b = 5a - 5b
⇒ 2a = 8b
⇒ a = 4b,
⇒ a/b = 4/1

Now, ( a² + b² ) / (a² - b² ) = [a² / (b²+1)] / [a² / (b² -1)]
= [( a/b )² + 1] / [( a/b )² - 1] = [( 4/1 )² + 1] / [( 4/1 )² - 1]
= [16 + 1] / [16 - 1] = 17/15

Correct Option: A

(a + b) / (a - b) = 5/3
⇒ 3a + 3b = 5a - 5b
⇒ 2a = 8b
⇒ a = 4b,
⇒ a/b = 4/1

Now, ( a² + b² ) / (a² - b² ) = [a² / (b²+1)] / [a² / (b² -1)]
= [( a/b )² + 1] / [( a/b )² - 1] = [( 4/1 )² + 1] / [( 4/1 )² - 1]
= [16 + 1] / [16 - 1] = 17/15
∴ ( a² + b² ) : ( a² - b² ) = 17 : 15

Given that, x/2y = 6/7
⇒ x/y = 12/7
By componenod dividendo,
(x - y) / (x + y) = (12 - 7) / (12 + 7) = 5/19

Correct Option: B

Given that, x/2y = 6/7
⇒ x/y = 12/7
By componenod dividendo,
(x - y) / (x + y) = (12 - 7) / (12 + 7) = 5/19
∴ (x - y) / (x + y) + 14 /19 = 5/19 + 14/19 = 19/19 = 1

Given that
Sanjay + Suresh = 120 ...(i)
Sanjay - Suresh = 30 ...(ii)
By adding Eqs (I) and (ii) we get
2 x sanjay = 150
∴ sanjay = 150/2 = 75 kg
∴ Weight of Suresh = 75 - 35 = 45 kg

Correct Option: B

Given that
Sanjay + Suresh = 120 ...(i)
Sanjay - Suresh = 30 ...(ii)
By adding Eqs (I) and (ii) we get
2 x sanjay = 150
∴ sanjay = 150/2 = 75 kg
∴ Weight of Suresh = 75 - 35 = 45 kg
∴ Suresh : Sanjay = 45 : 75 = 3 : 5 = 3/5 = 0.6