A cylindrical glass beaker of diameter 7 cm contains water. How many spherical glass marbles, each of diameter 1.4 cm, must be dropped in to raise the water level by 5.6 cm? Take $\pi = \frac{22}{7}$.

Explanation

1. 01

   Extra water level: $\pi \times 3.5^2 \times 5.6 = 68.6\pi$ cm³.

2. 02

   One marble: $\frac{4}{3}\pi \times 0.7^3 = \frac{4}{3}\pi \times 0.343$ cm³.

3. 03

   Number = $68.6 \div \left(\frac{4}{3} \times 0.343\right) = 68.6 \times 3 \div 1.372 = 150$.