**Let us consider number of days as ‘x’ days**

Weight of dust (kg) | 1.2 × 10^{8} | 4.8 × 10^{8} |

| 15 | x |

(1.2 × 10^{8})/15 = (4.8 × 10^{8})/x

**By cross-multiplying**

(1.2 × 10^{8}) x = (4.8 × 10^{8}) × 15

x = (4.8 × 10^{8 }× 15) / (1.2 × 10^{8})

= 60

**∴ The dust of 4.8 × 10**^{8} kg will be picked up in 60 days from the atmosphere.