Calculate Hourly Rate: 3 Glasses × 13 Hours Water Consumption Problem

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

Because Danny drinks 3 glasses every hour for 13 hours! Think of it as repeated addition: 3 + 3 + 3... (13 times) = 3 × 13 = 39 glasses.

Q: How can I check if my answer makes sense?

Use estimation! Danny drinks 3 glasses per hour, so in 10 hours he'd drink about 30 glasses. In 13 hours, it should be a bit more than 30, so 39 makes sense.

Q: What if Danny drank different amounts each hour?

Then you'd need to add up each individual hour instead of using multiplication. Multiplication only works when the rate stays constant.

Q: Can I use this method for other rate problems?

Speed: Distance = Speed × TimeMoney: Total cost = Price per item × Number of itemsWork: Total work = Work rate × TimeThe pattern is always the same!

Rate Multiplication with Time Intervals

Danny drinks three glasses of water per hour.

How many glasses of water does Danny drink in 13 hours?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:06 Let's find out how many cakes Danny will eat in 13 hours.

00:11 We know the number of cakes he eats per hour and the total hours.

00:17 We'll use long multiplication to figure it out.

00:20 First, solve each part of the multiplication, step by step. Then, put it all together.

00:36 And that's how we find the answer to our question.

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

Danny drinks three glasses of water per hour.

How many glasses of water does Danny drink in 13 hours?

Step-by-step solution

The problem requires us to find out how many glasses of water Danny drinks in 13 hours given he drinks 3 glasses per hour. Our task is to multiply the number of glasses Danny drinks per hour by the number of hours he continues this rate.

Step 1: Identify the rate: Danny drinks 3 glasses per hour.
Step 2: Determine the duration: 13 hours.
Step 3: Apply multiplication to find the total glasses consumed:

To find the total number of glasses:

$\text{Total glasses} = 3 \, (\text{glasses per hour}) \times 13 \, (\text{hours})$

Calculating the product:

$3 \times 13 = 39$

Therefore, Danny drinks a total of 39 glasses of water over the span of 13 hours.

Final Answer

$39$

Key Points to Remember

Essential concepts to master this topic

Rate Formula: Total = Rate per unit × Number of units
Technique: Identify rate (3 glasses/hour) and multiply by time (13 hours)
Check: Verify by dividing total glasses by hours: 39 ÷ 13 = 3 ✓

Common Mistakes

Avoid these frequent errors

Adding rate and time instead of multiplying
Don't add 3 + 13 = 16 glasses! This ignores the fact that Danny drinks 3 glasses every single hour for 13 consecutive hours. Always multiply the rate by the total time period.

Practice Quiz

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FAQ

Everything you need to know about this question

Why do I multiply instead of add the numbers?

Because Danny drinks 3 glasses every hour for 13 hours! Think of it as repeated addition: 3 + 3 + 3... (13 times) = 3 × 13 = 39 glasses.

What if the problem asked for glasses per day instead?

You'd need to know how many hours are in a day (24), then calculate: $3 \times 24 = 72$ glasses per day.

How can I check if my answer makes sense?

Use estimation! Danny drinks 3 glasses per hour, so in 10 hours he'd drink about 30 glasses. In 13 hours, it should be a bit more than 30, so 39 makes sense.

What if Danny drank different amounts each hour?

Then you'd need to add up each individual hour instead of using multiplication. Multiplication only works when the rate stays constant.

Can I use this method for other rate problems?

Speed: Distance = Speed × Time
Money: Total cost = Price per item × Number of items
Work: Total work = Work rate × Time

The pattern is always the same!

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