## Key Concepts

- Use a bar diagram to solve a multiplication problem

### Solve word problems using multiplication

**What are the steps in solving word problems involving multiplication?**

- Read and understand the problem.

- Know what is asked.

- Find what the given parts are.

- Determine what operation to be used and take the word clue that will represent multiplication.

- Solve the problem.

- Verify the answer.

**Example:**

The monthly salary of a man is $2,625. Find the annual income.

**Solution:**

Monthly income = $2,625

Annual income = $2,625 × 12

Therefore, annual income = $31,500.[Text Wrapping Break]**3.7.1 Use a bar diagram to solve a multiplication problem**

### Bar diagram

Bar diagrams are the pictorial representation of data (generally grouped) in the form of vertical or horizontal rectangular bars.

**Example:**

Uncle Ray is 3 times as old as Lenin. Lenin is 13 years old. Find the age of Uncle Ray.

**Solution:**

What am I asked to find?

Let a = The age of the uncle.

Draw a bar diagram to represent the problem.

Write and solve the equation using the variable.

13 x 3 = a

39 = a

Uncle age = 39.

**Example 2:**

Charmin bought 6 Fun Fest tickets. Each one cost $135. What is the total cost?

**Solution:**

What am I asked to find?

Let p = The cost of 6 tickets.

Draw a bar diagram to represent the problem.

Write and solve equation using the variable.

$135 x 6 = p

$135 x 6 =$ 810

So, p =$ 810

6 Fun Fest tickets cost is $ 810.

**Example 3:**

Sharon’s Stationery store has 1,219 boxes of cards. May’s market has 3 times as many boxes of cards. Find the total cards May’s market have.

**Solution:**

What am I asked to find?

Let b= boxes of cards.

Draw a bar diagram to represent the problem.

Write and solve the equation using the variable.

1,219 x 3 = b

1,219 x 3 = 3,657.

May’s market has 3,657 boxes of cards.

## Exercise

- The capacity of a drum is 50 liters of milk. How much milk can be collected in 5 drums of such capacity?
- In a school, a fee of $1,345 is collected per student. If there are 24 students in a class, how much fee is collected from that class?
- A train has 14 coaches. In each coach, there are 172 seats. Find the total number of such seats on the train.
- Lenin bought a room-cooler. The cost of the room-cooler is $1958. Find the total cost of 5 such room-coolers.
- One watch costs $896. Find the cost of 10 such watches.
- 18 theaters are there at the mall. Each theater has 175 seats. How many seats are there in all?

- 2,456 x 7 = p. Find the value of p.
- 134 x 34=_______.
- 3,145 x 5 =_________.
- ____ x 98 =98,000

### Concept Map

### What have we learned

- Understand how to solve word problems.
- Identify bar diagram.
- Use a bar diagram to solve a multiplication problem.
- Understand how to solve equation using variable.