Question

The problem states: there are 9 more pencils than pens in a container. There are 25 writing utensils in the container in all. How many pens are there in the container?

Let p represent the number of pens

Which equation represents the situation?

A: 2(p+9)=25

B: 2p+9=25

C: 2p-9=25

D:p+9=25

Answer 1

2p+9=25
2p=25-9
2p = 16
p = 8

You can prove this is true because
8 pens plus 8+9 pencils are 25

Answer 2

The right answer is 2p + 9 = 25

According to this problem, we know:

• p represents the number of pens.
• There are 25 writing utensils in a container in all.
• There are pens and pencils in the container in all.

The statement there are nine more pencils than pens in the container can be written as follows:

(1) P = p + 9

where:

P: Number of pencils

p: Number of pens

There are 25 writing utensils in the container in all, therefore:

(2) p + P = 25

Matching these two equations, we have:

(1) P = p + 9

(2) p + P = 25

Substituting (1) in (2):

p + (p+9) = 25

∴ 2p + 9 = 25

Therefore:

2p = 16 ∴ p = 8

and P

P = p + 9 ∴ P = 17

Finally:

There are 8 pens and 17 pencils in the container.