Chapter 5

Relationships in Time

See how seconds, minutes, hours, days, weeks and years fit together.

Units of Time

Time is measured with different units. Small units join to make bigger ones. Knowing how they fit together helps us change one unit into another.

Key idea

1 minute = 60 seconds · 1 hour = 60 minutes · 1 day = 24 hours · 1 week = 7 days · 1 year = 12 months

Changing Units

To change a bigger unit into a smaller unit, we multiply. For example, 3 hours = 3 × 60 = 180 minutes. To change a smaller unit into a bigger unit, we divide.

Worked example

How many days are in 2 weeks? One week has 7 days, so 2 weeks = 2 × 7 = 14 days. To go back: 14 days ÷ 7 = 2 weeks.

Remember

  • Bigger unit to smaller unit: multiply.
  • Smaller unit to bigger unit: divide.
  • 1 year is about 365 days.

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