Subject: General Aptitude · Chapter: Volume and Surface Area · Exam: · Marks: · Difficulty:
An open box is made of wood 3 cm thick. Its external dimensions are 1.46 m, 1.16 m and 8.3 dm. The cost of painting the inner surface of the box at 50 paise per 100 sq. cm is
(a)₹ 138.50
(b)₹ 277
(c)₹ 415.50
(d)₹ 554
Answer
Answer (as printed): B
Explanation
Internal length $=(146-6) \mathrm{cm}=140 \mathrm{cm}$. Internal breadth = (116-6) cm = 110 cm. Internal depth $=(83-3) \mathrm{cm}=80 \mathrm{cm}$. Area of inner surface $=[2(l+b) \times h]+l b$ $$=[2(140+110) \times 80+140 \times 110] \mathrm{cm}^{2}=55400 \mathrm{cm}^{2} .$$ ∴ Cost of painting $=₹\left(\frac{1}{2} \times \frac{1}{100} \times 55400\right)=₹ 277$.