Elapsed Time

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Concept Review

Elapsed Time: Your Personal Time Machine

What if you could travel forward in time? That's exactly what happens when you figure out elapsed time. When you know where you start and how long your journey takes, you can discover exactly when you'll arrive.

Think of time like a number line that never stops moving forward. Every minute, every hour takes you to a new point on this endless timeline. When we find elapsed time, we're taking a mathematical trip from one point to another.

The Time Travel Formula

Finding the end time is like solving a puzzle with three pieces:

Start Time + Duration = End Time

Where you begin + How long it takes = Where you finish

Let's take a real trip through time. Maya starts her soccer practice at 2:30 PM. Practice lasts for 1 hour and 45 minutes. When does practice end?

Start: 2:30 PM

Duration: 1 hour 45 minutes

↓

End: 4:15 PM

Here's how we solve it step by step: First, add the hour: 2:30 PM + 1 hour = 3:30 PM. Then add the minutes: 3:30 PM + 45 minutes = 4:15 PM. Maya's practice ends at 4:15 PM.

⚡ Time Crossing Secret

Sometimes your time journey crosses into the next hour! If you start at 3:45 PM and add 30 minutes, you don't get 3:75 PM (that doesn't exist!).

Instead: 3:45 PM + 30 minutes = 4:15 PM

Remember: when minutes go past 60, they "roll over" into the next hour, just like a car's odometer.

Your Time Navigation Tools

Professional time travelers (like you!) use different tools: analog clocks help you "see" the time moving forward, while digital clocks make the math crystal clear. Number lines can show your journey from start to finish, and even your fingers can count off the hours and minutes.

🔑 Key Takeaway

Every time you figure out when something ends, you're becoming a master time traveler. You're not just doing math — you're controlling time itself, using the power of addition to journey from any starting point to your exact destination in the future.

Sample questions

1. Pluto starts a program at 2:00 P.M. It runs for 45 minutes. What time does it finish?

✓ 2:45 P.M.

○ 3:00 P.M.

○ 2:30 P.M.

○ 1:15 P.M.

Answer: 2:45 P.M. — Add the duration (45 mins) to the start time ($2:00$).

2. Abe starts a meeting at 10:15 A.M. It lasts for 1 hour and 10 minutes. When does it end?

○ 11:15 A.M.

✓ 11:25 A.M.

○ 12:25 P.M.

○ 11:30 A.M.

Answer: 11:25 A.M. — First add the hour ($11:15$), then add the 10 minutes ($11:25$).

3. A drone flight begins at 4:30 P.M. and lasts for 25 minutes. What time does it land?

○ 5:00 P.M.

○ 4:45 P.M.

✓ 4:55 P.M.

○ 5:30 P.M.

Answer: 4:55 P.M. — $30 + 25 = 55$. The hour remains the same.

Skills in this topic

Find the end time when given start time and duration
Find the start time when given end time and duration
Calculate elapsed time in minutes using a number line
Calculate elapsed time crossing the hour mark
Solve real-world word problems involving elapsed time

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