Earth's mass is $6 \times 10^{24}$ kg and the Moon's is $7.4 \times 10^{22}$ kg, separated by $3.84 \times 10^8$ m. With $G = 6.7 \times 10^{-11}$ N m$^2$ kg$^{-2}$, the gravitational force between them is about:

1. Use $F = \dfrac{G m_1 m_2}{r^2}$ with $r = 3.84\times10^8$ m (since $3.84\times10^5$ km $= 3.84\times10^8$ m). 2. Numerator $= 6.7\times10^{-11}\times6\times10^{24}\times7.4\times10^{22} = 2.975\times10^{37}$. 3. Denominator $r^2 = (3.84\times10^8)^2 = 1.475\times10^{17}$. 4. $F = \dfrac{2.975\times10^{37}}{1.475\times10^{17}} \approx 2\times10^{20}$ N. 5. Mis-converting km to m shifts the exponent and produces the trap options. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 1 "Gravitation", p.24_