In how many ways can 4 books be arranged on a shelf if there are 8 books to choose from?

1680 ways

Step-by-step explanation:

By using the formula for permutation, which is nPr=n!/(n-r)!,

8P4=8!/(8-4)!

=8!/4!

=8×7×6×5

=1680

Or if you just want to use the multiplication rule (which is simpler).

8×7×6×5=1680

answer: city needs 2.4 inches of rainfall more to match the record of 40 inches.

step-by-step explanation:

since we have given that

total annual rainfall a city record = 40 inches

this year, total rainfall recorded = 37.6 inches

number of inches of rainfall   is needed to match the record of 40 inches is given by

hence, city needs 2.4 inches of rainfall more to match the record of 40 inches.

24 units

step-by-step explanation: