KnowledgeBoat Logo
|

Mathematics

The base radius of two right circular cone of the same height are in ratio 3 : 5.

Assertion(A): The ratio between their volume is 9 : 25.

Reason(R): As

r1r2=35πr12hπr22h=r12r22=(35)2\dfrac{r1}{r2} = \dfrac{3}{5} \\[1em] \dfrac{πr1^2h}{πr2^2h} = \dfrac{r1^2}{r2^2} = \Big(\dfrac{3}{5}\Big)^2 \\[1em]

  1. A is true, R is false.

  2. A is false, R is true.

  3. Both A and R are true and R is correct reason for A.

  4. Both A and R are true and R is incorrect reason for A.

Mensuration

2 Likes

Answer

Given, the base radius of two right circular cone of the same height are in ratio 3 : 5.

As we know that volume of cone = 13πr2h\dfrac{1}{3}πr^2h

Volume of 1st coneVolume of 2nd cone=13πr12h13πr22h=πr12hπr22h=r12r22=3252=(35)2=925.\dfrac{\text{Volume of 1st cone}}{\text{Volume of 2nd cone}} = \dfrac{\dfrac{1}{3}πr1^2h}{\dfrac{1}{3}πr2^2h}\\[1em] = \dfrac{πr1^2h}{πr2^2h}\\[1em] = \dfrac{r1^2}{r2^2}\\[1em] = \dfrac{3^2}{5^2}\\[1em] = \Big(\dfrac{3}{5}\Big)^2\\[1em] = \dfrac{9}{25}.

∴ Both A and R are true and R is correct reason for A.

Hence, option 3 is the correct option.

Answered By

1 Like


Related Questions