Question

37. Two years ago, Bob flew 6 x 105 miles in an airplane. This was 15 times as many
miles as he flew last year.
How many miles did Bob fly last year?
A. 4* 104 miles
B. 4 x 106 miles
C. 9 x 104 miles
D. 9 * 106 miles

Answer 1

Answer:

  A.  4·10⁴

Step-by-step explanation:

The problem statement tells you ...

  6×10⁵ miles = 15 × (last year's mileage)

Dividing by 15 gives ...

  (60×10⁴ miles)/15 = (last year's mileage) = 4×10⁴ miles

_____

Further explanation

An exponent is an indication of repeated multiplication.

  10⁵ = 10·10·10·10·10 = 100,000

We can use the associative property of multiplication to rewrite the number of miles:

  6×10⁵ = 6·(10·10·10·10·10) = 600,000 = (6·10)·(10·10·10·10) = 60×10⁴