Question

A small plant is 212 inches tall. How tall will it be in 3 weeks if it grows 34 inch each week? Which method will NOT give the correct number of inches?

Answer 1

Answer:

Multiply $2\frac{1}{2}$ by $3$ and then add $\frac{3}{4}$

Step-by-step explanation:

we know that

using proportion

$\frac{(3/4)}{1}\frac{in}{week}=\frac{x}{3}\frac{in}{weeks} \\ \\x=3*(3/4)\\ \\x=9/4\ in$

Find the height of the plant in $3$ weeks

$2\frac{1}{2} +\frac{9}{4}=\frac{5}{2} +\frac{9}{4}\\ \\=\frac{19}{4}\ in$

therefore

The incorrect method is

Multiply $2\frac{1}{2}$ by $3$ and then add $\frac{3}{4}$

because

$2\frac{1}{2}*3+\frac{3}{4}=\frac{15}{2}+\frac{3}{4}\\ \\=\frac{33}{4}\ in$