Question

The dimensions of a brick and a wall are \(20\text{ cm} \times 10\text{ cm} \times 7.5\text{ cm}\) and \(25\text{ m} \times 2\text{ m} \times 0.75\text{ m}\) respectively. How many bricks (in thousands) are required to construct the wall?

• A. \(26\)
• B. \(25\)
• C. \(40\)
• D. \(20\)

Hint:

Number of bricks required \[ = \frac{\text{Volume of wall}}{\text{Volume of one brick}}. \] Always convert all measurements into the same unit first.

Answer 1

The Correct Option is B

Step 1: Find the volume of the wall. Convert into centimeters: \[ 25\text{ m}=2500\text{ cm} \] \[ 2\text{ m}=200\text{ cm} \] \[ 0.75\text{ m}=75\text{ cm} \] Thus, \[ V_w=2500\times200\times75 \] \[ =37500000 \] cm\(^3\).

Step 2: Find volume of one brick. \[ V_b=20\times10\times7.5 \] \[ =1500 \] cm\(^3\).

Step 3: Calculate number of bricks. \[ \frac{37500000}{1500} = 25000 \] Thus the number of bricks is \[ 25000 \] which means \[ 25 \] thousand bricks. \[ \boxed{25} \]