Question

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Answer 1

US postal service delivered = 7.14 x 10^10 pieces of mail in December.

US postal service delivered = 3.21 x 10^10 pieces of mail in January.

We need to find the total number of mail delivered in both months.

In the shown work you setup problem correctly.

You are adding

7.14 x 10^10

3.21 x 10^10

_____________

10.35 x10^10

You got 10.35 x10^10 on adding.

Therefore, second step is correct too.

But in third step when you moved decimal one place on left you wrote 1.035 x 10^10.

Error: When we move decimal one place on left the exponent of 10 should be raised to one.

Correct work: After moving decimal one place on we would get left 1.035 x 10^11.

Strategy used: Moving decimal one place left raise the power 10 to one and moving decimal place right decrease the power 10.