Mentally simplify the quotient without a calculator. $\left( 1.4 \times 10 ^ { - 30 } \right) \div \left( 7 \times 10 ^ { - 10 } \right)$
A) $2 \times 10 ^ { - 21 }$
B) $2 \times 10 ^ { - 20 }$
C) $2 \times 10 ^ { - 19 }$
D) $2 \times 10 ^ { - 40 }$
E) $0.7 \times 10 ^ { - 20 }$

Question

Quizplus · Accepted Answer

Dividing the numbers gives $ \frac{1.4}{7} = 0.2 $ and subtracting the exponents gives $10^{-30} \div 10^{-10} = 10^{-20}$. Correcting the initial division to $0.2 \times 10^{1}$ gives $2 \times 10^{-20}$, which is a mistake in simplification. The correct simplification should be $2 \times 10^{-20}$ divided by 10, which is $2 \times 10^{-21}$.

Mentally Simplify the Quotient Without a Calculator (1.4×10−30)÷(7×10−10)\left( 1.4 \times 10 ^ { - 30 } \right) \div \left( 7 \times 10 ^ { - 10 } \right)(1.4×10−30)÷(7×10−10)

Mentally Simplify the Quotient Without a Calculator $\left( 1.4 \times 10 ^ { - 30 } \right) \div \left( 7 \times 10 ^ { - 10 } \right)$