Question

Which of the following is a reasonable estimate for the weight of an 18-wheeler truck?

A.
8 × 10-4 lb
B.
8 × 102 lb
C.
8 × 10-2 lb
D.
8 × 104 lb

Answer 1

By moving the decimal according to the number of places expressed by the exponents, we can see the real value of each answer choice.

A. .0008 lbs not a realistic weight for an 18-wheeler

B. 800 lbs closer but still not enough weight

C. .08 nope not this one either.

D. 80,000 lbs. this is probably in the range we are looking for.

If the exponent is negative, move the decimal that many spaces left. If the exponent is positive, move the decimal that many space right.

The correct answer is D.

Answer 2

The reasonable estimate for the weight of an 18-wheeler is
`8 * 10^(4) lb`

Explanation:

The average and legally maximum weight of an 18-wheeler is 80,000 pounds.

From option a through d, we check which of the measurement is close or equivalent to 80,000 pounds

• 
  `8 * 10^(-4)`

By converting this, we have

`= 8 * (1)/(10000) lb`

`= (8)/(10000) lb`

`= 0.0008 lb`

• 
  `8 * 10^(2)`

By converting this, we have

`= 8 * 100 lb`

`= 800 lb`

• 
  `8 * 10^(-2)`

By converting this, we have

`= 8 * (1)/(100) lb`

`= (8)/(100) lb`

`= 0.08 lb`

• 
  `8 * 10^(4)`

By converting this, we have

`= 8 * {10000} lb`

`= {80000} lb`

From the 4 conversions, only
`8 * 10^(4) lb` is equivalent to the average and legally maximum weight of an 18-wheeler, 80,000 pounds.

Hence, the reasonable estimate for the weight of an 18-wheeler is
`8 * 10^(4) lb`