Time and Money Calculations

In fifth grade, you will often solve real-world problems that involve tracking time and calculating money. These problems usually require multiple steps, like converting units, finding how much time has passed, or figuring out exact change.

Calculating Elapsed Time

Elapsed time is the amount of time that passes from the start of an event to its end. A great way to find elapsed time is by breaking the time into manageable chunks.

Example: A flight departs at 8:45 AM and arrives at 2:15 PM. How long is the flight?

1. Count from 8:45 AM to the next whole hour (9:00 AM) $\rightarrow$ $15$ minutes.
2. Count the hours from 9:00 AM to 2:00 PM $\rightarrow$ $5$ hours.
3. Count the remaining minutes from 2:00 PM to 2:15 PM $\rightarrow$ $15$ minutes.
4. Add them together: $5 \text{ hours} + 15 \text{ minutes} + 15 \text{ minutes} = 5 \text{ hours and } 30 \text{ minutes}$.

Converting Time Units

Sometimes you need to convert between days, hours, minutes, and seconds. Remember your basic conversions:

• $1 \text{ day} = 24 \text{ hours}$
• $1 \text{ hour} = 60 \text{ minutes}$
• $1 \text{ minute} = 60 \text{ seconds}$

Example: Convert $3.5$ hours to hours and minutes.

• The whole number is the hours: $3$ hours.
• The decimal is the fraction of an hour: $0.5 \text{ hours}$.
• Multiply the decimal by $60$ to find the minutes: $0.5 \times 60 = 30 \text{ minutes}$.
• Answer: $3$ hours and $30$ minutes.

Money Calculations

When calculating money, always remember to line up the decimal points! You will frequently need to find totals, make change, or apply discounts.

Example: An item costs \24.99$with a$$5.00$ coupon. What is the final price?

• Set up the subtraction problem by aligning the decimals: $\$24.99 - \$5.00 = \$19.99$
• The final price is \19.99$.