# 3.3: How Many Pounds

**At Grade**Created by: CK-12

**How Many Pounds? – Equation Solving: Replace Variables with Their Values**

**Teacher Notes**

Given the weights of two blocks, students determine the total weight of various collections of these blocks. The key algebraic idea is that of replacement. To figure out the total weight of a collection of blocks, students record the weight of each block on that block (i.e. replacing it with its value), and then add to determine the total weight. These problems prepare students for the skill of substitution which is a major problem solving technique in the solution of algebraic equations.

**Solutions**

**How Many Pounds? 1**

- 7 pounds
- 11 pounds
- 14 pounds

**How Many Pounds? 2**

- 12 pounds
- 15 pounds
- 18 pounds

**How Many Pounds? 3**

- 20 pounds
- 18 pounds
- 22 pounds

**How Many Pounds? 4**

- 20 pounds
- 19 pounds
- 30 pounds

**How Many Pounds?**

(Teacher Page)

Figure out the total number of pounds.

\begin{align*}\begin{aligned}& \mathbf{Describe:} && \text{Three scales with blocks.}\\ &&& \mathbf{A:} \ \text{one cube is} \ 4 \ \text{pounds.}\\ &&& \mathbf{B:} \ \text{one cylinder is} \ 2 \ \text{pounds.}\\ &&& \mathbf{C:} \ \text{one cube and} \ 2 \ \text{cylinders. No number of pounds.}\\ & \mathbf{My \ Job:} && \text{Figure out the total number of pounds for scale} \ C.\\ & \mathbf{Plan:} && \text{Write the numbers of pounds on the blocks on} \ C.\\ &&& \text{Add to figure out the total number of pounds.}\\ & \mathbf{Solve:}\end{aligned} \end{align*}

\begin{align*}\begin{aligned} \mathbf{Check:} && 4 + 2 + 2 = 8 \end{aligned}\end{align*}

**How Many Pounds 1**

Figure out the total number of pounds.

Write the number on the scale.

**How Many Pounds 2**

Figure out the total number of pounds.

Write the number on the scale.

**How Many Pounds? 3**

Figure out the total number of pounds.

Write the number on the scale.

**How Many Pounds? 4**

Figure out the total number of pounds.

Write the number on the scale.

**Extras for Experts: How Many Pounds?**

**Solutions**

**Extra for Experts: How Many Pounds? 1**

- 30 pounds
- 23 pounds
- 40 pounds

**Extra for Experts: How Many Pounds? 2**

- 19 pounds
- 20 pounds
- 26 pounds

**Extra for Experts: How Many Pounds? 1**

Figure out the total number of pounds.

Write the number on the scale.

**Extra for Experts: How many pounds? 2**

Figure out the total number of pounds.

Write the number on the scale.

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Jan 18, 2013## Last Modified:

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