Question

A supermarket has 148 shrubs on their property, but they are having trouble mowing grass so they need to pay to have cut down shrubs each year until the property has less than 30 shrubs. If they can pay to have only three shrubs cut down this year, but six shrubs cut down every year after that, in how many years will they have less than 30 shrubs on their property?

Answer 1

21 years.

Explanation:

All equations are written in bold so you can find them easier.

The first thing we do is subtract the 3 shrubs from the first year from the total 148.

148 - 3 = 145

We then take 29 from 145, as the supermarket wants less than 30 shrubs on their property, so the maximum amount they want to keep is actually 29.

145 - 29 = 116

The supermarket can pay to have 6 shrubs cut down every year, excluding the first, so we need to do then is divide 116 by 6.

116 ÷ 6 = 19.333.

Because that equation leaves us with a decimal, we have to round up to get a whole number because the answer has to be in years, not years and months.

19.333 rounded up is 20.

So that's 20 years of paying for 6/per year. We have to add on the one year they only payed for 3 shrubs to be cut down, making the answer;

21 years.

We can further confirm we have the right answer by doing;

6 × 20 = 120

145 - 120 = 25

Because we're going down in 6's, we know that 20 is the lowest amount of years it would take to get less than 30 shrubs, because 25 + 6 = 31.

Answer 2

Answer: 21 years

Step-by-step explanation: After the first year, it’s down by 3 so 145. For the next 20 years, you go down 6 shrubs a year. At year 20 it will be 31 shrubs so at year 21 it will be at 25 shrubs.