Question

the surface area of a cube is equal to the sum of the surface areas of three other cubes whose edges are 3 cm 4 cm and 12 CM respectively find the edge of the first cube​

Answer 1

hope it helps..........

Answer 2

The edge of first cube is 13 cm

Solution:

The formula for surface area of cube is:

$S.A = 6a^2$

Where, "a" is the length of side of cube

Given that,

The surface area of a cube is equal to the sum of the surface areas of three other cubes whose edges are 3 cm 4 cm and 12 cm

Therefore,

$\text{S.A of first cube }= 6(3)^2 + 6(4)^2 + 6(12)^2\\\\\text{S.A of first cube }= 6(9 + 16 + 144)\\\\\text{S.A of first cube }= 6 \times 169\\\\\text{S.A of first cube }=1014$

Let "x" be the edge of first cube

Then,

$6x^2 = 1014\\\\x^2 = \frac{1014}{6}\\\\x^2 = 169\\\\x = 13$

Thus the edge of first cube is 13 cm

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