Question

Millie needs the average height of the plants she is buying to be at least 73 inches. She has selected three plants that are 70, 71 and 72 inches tall. Write and solve an inequality that Millie could use to determine the possible heights of her fourth plant

Answer 1

`(70+71+72+x)/(4)\geq 73`

`x\geq 79`

Step-by-step explanation:

Let x be the height of 4th plant purchased by Millie.

We have been given that Millie needs the average height of the plants she is buying to be at least 73 inches. She has selected three plants that are 70, 71 and 72 inches tall.

So the average of 4 plants purchased by Millie will be:
`(70+71+72+x)/(4)`

We can represent this information in an inequality as:
`(70+71+72+x)/(4)\geq 73`

Therefore, our desired inequality will be
`(70+71+72+x)/(4)\geq 73`.

Now let us solve our inequality by multiplying both sides of inequality by 4.

`4*(70+71+72+x)/(4)\geq 4*73`

`70+71+72+x\geq 292`

`213+x\geq 292`

`x\geq 292-213`

`x\geq 79`

Therefore, the height of 4th plant purchased by Millie must be at least 79 inches.