Lateral area to breadth of a cuboid:\nThe area of four walls (lateral surface) of a cuboid is 400 cm². If its length is 15 cm and height is 8 cm, find the breadth (in cm).

Introduction / Context:
The “area of 4 walls” of a cuboid is its lateral surface area (LSA), given by 2h(l + b), where l is length, b is breadth, and h is height. Knowing LSA, l, and h allows solving for b directly.

Given Data / Assumptions:

• LSA = 400 cm².
• l = 15 cm; h = 8 cm.

Concept / Approach:
Use LSA = 2h(l + b). Rearrange to isolate (l + b) = LSA / (2h). Then b = (LSA / (2h)) − l. Substitute known values carefully to avoid arithmetic errors.

Step-by-Step Solution:

Verification / Alternative check:
Compute LSA back: 2*8*(15 + 10) = 16*25 = 400 cm², confirming the value.

Why Other Options Are Wrong:
12, 20, 24 correspond to mis-divisions (e.g., dividing by 8 instead of 16) or forgetting to subtract l from the sum.

Common Pitfalls:
Confusing total surface area with lateral surface area; using 2(l + b) without multiplying by h and 2.

Final Answer:
10