Skip to main contentSkip to solution

V1,V2,V3V_1, V_2, V_3 and V4V_4 are the volumes of four cubes of side lengths x cm, 2x cm, 3x cm and 4x cm respectively. The following statements regarding these volumes are given below.

(A) V1+V2+2V3<V4V_1 + V_2 + 2V_3 < V_4

(B) V1+3V2>V3+V4V_1 + 3V_2 > V_3 + V_4

(C) 2(V1+V3)+V2=V42(V_1 + V_3) + V_2 = V_4

(D) V1+4V2+V3<V4V_1 + 4V_2 + V_3 < V_4

Which of these statements is/are correct?

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

The four cubes have side lengths xx cm, 2x2x cm, 3x3x cm, and 4x4x cm.

Volume of a cube =(side)3= \text{(side)}^3

V1=x3V_1 = x^3

V2=(2x)3=8x3V_2 = (2x)^3 = 8x^3

V3=(3x)3=27x3V_3 = (3x)^3 = 27x^3

V4=(4x)3=64x3V_4 = (4x)^3 = 64x^3

Quick tip: When you cube a number with xx, cube the number separately. For example, (2x)3=23×x3=8x3(2x)^3 = 2^3 \times x^3 = 8x^3

Super shortcut: Since all volumes have x3x^3 in common, we can just compare the coefficients: 1,8,27,641, 8, 27, 64


Statement (A): V1+V2+2V3<V4V_1 + V_2 + 2V_3 < V_4

Left side:

V1+V2+2V3=x3+8x3+2(27x3)=x3+8x3+54x3=63x3V_1 + V_2 + 2V_3 = x^3 + 8x^3 + 2(27x^3) = x^3 + 8x^3 + 54x^3 = 63x^3

Right side: V4=64x3V_4 = 64x^3

Since 63x3<64x363x^3 < 64x^3, Statement (A) is TRUE.


Statement (B): V1+3V2>V3+V4V_1 + 3V_2 > V_3 + V_4

Left side:

V1+3V2=x3+3(8x3)=x3+24x3=25x3V_1 + 3V_2 = x^3 + 3(8x^3) = x^3 + 24x^3 = 25x^3

Right side:

V3+V4=27x3+64x3=91x3V_3 + V_4 = 27x^3 + 64x^3 = 91x^3

Since 25x3≯91x325x^3 \not> 91x^3, Statement (B) is FALSE.


Statement (C): 2(V1+V3)+V2=V42(V_1 + V_3) + V_2 = V_4

Left side:

2(V1+V3)+V2=2(x3+27x3)+8x3=2(28x3)+8x3=56x3+8x3=64x32(V_1 + V_3) + V_2 = 2(x^3 + 27x^3) + 8x^3 = 2(28x^3) + 8x^3 = 56x^3 + 8x^3 = 64x^3

Right side: V4=64x3V_4 = 64x^3

Since 64x3=64x364x^3 = 64x^3, Statement (C) is TRUE.


Statement (D): V1+4V2+V3<V4V_1 + 4V_2 + V_3 < V_4

Left side:

V1+4V2+V3=x3+4(8x3)+27x3=x3+32x3+27x3=60x3V_1 + 4V_2 + V_3 = x^3 + 4(8x^3) + 27x^3 = x^3 + 32x^3 + 27x^3 = 60x^3

Right side: V4=64x3V_4 = 64x^3

Since 60x3<64x360x^3 < 64x^3, Statement (D) is TRUE.


Statements (A), (C), and (D) are correct.

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question