Calculate Total Houses: Finding Product of 4 Streets × 20 Average Houses

Q: Why do I multiply instead of add the numbers?

Because 20 is the average per street, not the total! If each of the 4 streets has an average of 20 houses, you need 20 + 20 + 20 + 20 = 80 houses, which equals $ 4 \times 20 = 80 $.

Q: What does 'average' mean in this problem?

Average means the typical number of houses on each street. So if the average is 20, each street has approximately 20 houses (some might have 18, others 22, but they average to 20).

Q: How can I remember when to multiply vs add?

Ask yourself: "Is this per group or total?" When you see per (per street, per day, per person), multiply by the number of groups. When you see individual amounts to combine, add them.

Q: What if the streets had different numbers of houses?

Then you'd need the exact number for each street and add them up. But since we're given an average, we use multiplication because the average applies to all streets equally.

Q: Can I check my answer a different way?

Yes! Divide your total by the number of streets: $ 80 ÷ 4 = 20 $. This should equal the given average. If it matches, your answer is correct!

Multiplication Problems with Average Values

There are 4 streets in a neighbourhood.

If the average number of houses on each street is 20, then how many houses are there in the neighborhood altogether?

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Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

There are 4 streets in a neighbourhood.

If the average number of houses on each street is 20, then how many houses are there in the neighborhood altogether?

Step-by-step solution

To solve this problem, we’ll follow these steps:

Step 1: Determine the number of streets.
Step 2: Determine the average number of houses per street.
Step 3: Calculate the total number of houses by multiplying these two values.

Now, let's work through each step:

Step 1: The number of streets is given as 4.
Step 2: The average number of houses per street is 20.
Step 3: Using the formula $\text{Total number of houses} = \text{Average number of houses} \times \text{Number of streets}$ , we have:

$\text{Total number of houses} = 20 \times 4 = 80$

Therefore, the solution to the problem is $80$ .

Final Answer

$80$

Key Points to Remember

Essential concepts to master this topic

Formula: Total = Number of groups × Average per group
Calculation: Multiply 4 streets × 20 houses = 80 houses
Check: Does 80 ÷ 4 = 20 average houses per street? ✓

Common Mistakes

Avoid these frequent errors

Adding instead of multiplying the given values
Don't add 4 + 20 = 24 houses! This ignores that 20 is the average per street, not the total. You need 20 houses on each of the 4 streets. Always multiply: number of groups × average per group.

Practice Quiz

Test your knowledge with interactive questions

Calculate the average of $$ 10 $$ and $$ 12 $$ .

FAQ

Everything you need to know about this question

Why do I multiply instead of add the numbers?

Because 20 is the average per street, not the total! If each of the 4 streets has an average of 20 houses, you need 20 + 20 + 20 + 20 = 80 houses, which equals $4 \times 20 = 80$ .

What does 'average' mean in this problem?

Average means the typical number of houses on each street. So if the average is 20, each street has approximately 20 houses (some might have 18, others 22, but they average to 20).

How can I remember when to multiply vs add?

Ask yourself: "Is this per group or total?" When you see per (per street, per day, per person), multiply by the number of groups. When you see individual amounts to combine, add them.

What if the streets had different numbers of houses?

Then you'd need the exact number for each street and add them up. But since we're given an average, we use multiplication because the average applies to all streets equally.

Can I check my answer a different way?

Yes! Divide your total by the number of streets: $80 ÷ 4 = 20$ . This should equal the given average. If it matches, your answer is correct!

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