Examples with solutions for The Distributive Property for 7th Grade: Worded problems

Exercise #1

A building is 21 meters high, 15 meters long, and 14+30X meters wide.

Express its volume in terms of X.

(14+30X)(14+30X)(14+30X)212121151515

Step-by-Step Solution

We use a formula to calculate the volume: height times width times length.

We rewrite the exercise using the existing data:

21×(14+30x)×15= 21\times(14+30x)\times15=

We use the distributive property to simplify the parentheses.

We multiply 21 by each of the terms in parentheses:

(21×14+21×30x)×15= (21\times14+21\times30x)\times15=

We solve the multiplication exercise in parentheses:

(294+630x)×15= (294+630x)\times15=

We use the distributive property again.

We multiply 15 by each of the terms in parentheses:

294×15+630x×15= 294\times15+630x\times15=

We solve each of the exercises in parentheses to find the volume:

4,410+9,450x 4,410+9,450x

Answer

4410+9450x 4410+9450x

Exercise #2

In a fabric factory, the possible sizes of fabric are:

30x×(4x+8) 30x\times(4x+8)

(7+27x)×5 (7+27x)\times5

How much more material does the factory need?

Video Solution

Step-by-Step Solution

We begin by simplifying the two exercises using the distributive property:

We start with the first expression.

30x×(4x+8)= 30x\times(4x+8)=

30x×4x+30x×8= 30x\times4x+30x\times8=

120x2+240x 120x^2+240x

We now address the second expression:

(7+27x)×5= (7+27x)\times5=

5×7+5×27x= 5\times7+5\times27x=

35+135x 35+135x

In order to calculate the expressions, let's assume that in each expression x is equal to 1.

We can now substitute the X value into the equation:

120x2+240x=120×12+240×1=120+240=360 120x^2+240x=120\times1^2+240\times1=120+240=360

35+135×1=35+135=170 35+135\times1=35+135=170

Hence it seems that the first expression is larger and requires more fabric.

Let's now calculate the expressions assuming that x is less than 1. We substitute this value into each of the expressions as follows:x=110 x=\frac{1}{10}

120100+24010=115+24=2515 \frac{120}{100}+\frac{240}{10}=1\frac{1}{5}+24=25\frac{1}{5}

35+13510=48.5 35+\frac{135}{10}=48.5

This time the second expression seems to be larger and requires more fabric.

Therefore, it is impossible to determine.

Answer

It is not possible to calculate.

Exercise #3

A painter buys a canvas with the following dimensions:

(23x+12)×(20x+7) (23x+12)\times(20x+7)

How much space to paint does she have?

Video Solution

Step-by-Step Solution

We calculate the area using the distributive property:

23x×20x+23x×7+12×20x+12×7= 23x\times20x+23x\times7+12\times20x+12\times7=

We solve each of the multiplication exercises:

460x2+161x+240x+84= 460x^2+161x+240x+84=

We join the x coefficients:

460x2+401x+84= 460x^2+401x+84=

Answer

460x2+401x+84 460x^2+401x+84

Exercise #4

Gerard plans to paint a fence 7X meters high and 30X+4 meters long.

Gerardo paints at a rate of 7 m² per half an hour.

Choose the expression that represents the time it takes for Gerardo to paint one side of the fence.

30X+430X+430X+47X7X7X

Video Solution

Step-by-Step Solution

In order to solve the exercise, we first need to know the total area of the fence.

Let's remember that the area of a rectangle equals length times width.

Let's write the exercise according to the given data:

7x×(30x+4) 7x\times(30x+4)

We'll use the distributive property to solve the exercise. That means we'll multiply 7x by each term in the parentheses:

(7x×30x)+(7x×4)= (7x\times30x)+(7x\times4)=

Let's solve each term in the parentheses and we'll get:

210x2+28x 210x^2+28x

Now to calculate the painting time, we'll use the formula:

7m212hr=14m2hr \frac{7m^2}{\frac{1}{2}hr}=14\frac{m^2}{hr}

The time will be equal to the area divided by the work rate, meaning:

210x2+28x14 \frac{210x^2+28x}{14}

Let's separate the exercise into addition between fractions:

210x214+28x14= \frac{210x^2}{14}+\frac{28x}{14}=

We'll reduce by 14 and get:

15x2+2x 15x^2+2x

And this is Isaac's work time.

Answer

15x2+2x 15x^2+2x hours