Question

An orchard has 700 pear trees. The number of rows exceeds the number of trees per row by 3. How many trees are there in each row?

Answer 1

25

Explanation:

Number of rows: x

Number of trees per row: y

So x rows multiplied by y trees per row = 700

x × y = 700

xy = 700

This is our first equation

x rows = y trees per row plus three (or x rows minus three = y trees)

x = y + 3

So if x = y + 3,

In xy = 700, we can substitute the x because we have it's value

(y + 3)y = 700

y² + 3y = 700

Divide 3 by 2 then square the answer = 2.25

y² + 3y + 2.25 = 700 + 2.25

Simplify

(y + 1.5)² = 702.25

Get the square root of both sides

(y + 1.5) = ±26.5

y = 26.5 - 1.5 or -26.5 - 1.5

So y is either 25 or -28 (A negative number of trees doesn't make sense so we'll stick with 25