Time Conversions: Hours, Minutes, and Seconds
Time conversions between hours, minutes, and seconds rely on the factor-of-60 relationship: 1 hour = 60 minutes and 1 minute = 60 seconds, as taught in Grade 4 Pengi Math. Unlike the metric system’s base-10, time uses base-60, requiring students to multiply by 60 when converting to smaller units and divide by 60 when converting to larger units. Mastering this conversion is essential for solving elapsed-time problems, scheduling, and measurement word problems involving hours and minutes.
Key Concepts
Property The standard units of time are related by factors of 60. $1 \text{ hour} = 60 \text{ minutes}$ $1 \text{ minute} = 60 \text{ seconds}$.
Examples To convert 4 hours to minutes, you multiply by 60: $4 \text{ hours} \times 60 = 240 \text{ minutes}$. To convert 180 seconds to minutes, you divide by 60: $180 \text{ seconds} \div 60 = 3 \text{ minutes}$. To convert 2.5 minutes to seconds, you multiply by 60: $2.5 \text{ minutes} \times 60 = 150 \text{ seconds}$.
Explanation This skill covers the basic conversions between hours, minutes, and seconds. To convert a larger unit of time (like hours) to a smaller unit (like minutes), you multiply by 60. To convert a smaller unit (like seconds) to a larger unit (like minutes), you divide by 60. Mastering these conversions is a key first step for solving multi step problems involving time.
Common Questions
How many seconds are in an hour?
There are 3,600 seconds in one hour: 60 minutes per hour × 60 seconds per minute = 3,600 seconds.
How do you convert hours to minutes?
Multiply the number of hours by 60. For example, 2.5 hours = 2.5 × 60 = 150 minutes.
How do you convert minutes to hours?
Divide the number of minutes by 60. For example, 90 minutes = 90 ÷ 60 = 1.5 hours, or 1 hour and 30 minutes.
Why are there 60 seconds in a minute, not 100?
The base-60 system comes from ancient Babylonian mathematics. The number 60 is divisible by many numbers (1,2,3,4,5,6,10,12,15,20,30), making fractions of hours and minutes convenient.
How does time conversion appear in Grade 4 word problems?
Students solve elapsed-time problems (e.g., ‘How long from 2:35 PM to 4:10 PM?’) and unit conversion problems requiring a mix of hours and minutes in the same calculation.