Question

Assertion (A): The surface area of the cuboid formed by joining two cubes of sides 4 cm each, end-to-end, is 160 cm².

Reason (R): The surface area of a cuboid of dimensions I × b × h is (lb + bh + hl).

Options

• Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

• Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

• Assertion (A) is true, but Reason (R) is false.

• Assertion (A) is false, but Reason (R) is true.

Answer 1

Assertion (A) is true, but Reason (R) is false.

Explanation:

Assertion (A):

Side of each cube = 4 cm 

When two cubes are joined end-to-end, the dimensions of the resulting cuboid are:

Length (l) = 4 + 4 = 8 cm 

Breadth (b) = 4 cm

Height (h) = 4 cm

Surface area of cuboid = 2(lb + bh + hl)

= 2(8 × 4 + 4 × 4 + 4 × 8)

= 2(32 + 16 + 32)

= 2(80)

= 160 cm²

So, Assertion (A) is true.

Reason (R):

The formula for surface area of a cuboid is 2(lb + bh + hl). The given reason states (lb + bh + hl), which is incorrect.

So, Reason (R) is false.