When a rocket is launched straight up the distances in feet

When a rocket is launched straight up, the distances, in feet, that the rocket rises in each successive second before the second-stage ignition are given below. Is this sequence arithmetic? What is the common difference? What is the total distance the rocket rises in 15 sec?

21, 28, 35, 42, 49,....

Is this sequence arithmetic?

No

Yes

What is the common difference? Select the correct choice below and fill in the answer box within your choice if necessary.

A._____ft

B. The sequence is not arithmetic.

What is the total distance the rocket rises in 15sec?

____ft

Solution

Yes it is an arithmetic sequence.

21,(21+7)=28,(28+7)= 35,....,( 42+7) =49.....

The commom difference is 7 ft

28-21 =7

35-28 =7...

The rocket raises in 15 sec is (15*7) =105

total distance is(105- 21)=84 ft