Standard Units

Standard Units

GCSE(F),

It is often necessary to switch between different standard units: for example, moving from centimetres to metres. The table below shows the relationship between standard units.

When calculating larger changes: for example, changing kilometres to centimetres, it is often easier to carry out the calculation in two steps and using an intermediate value. For kilometres to centimetres, change the kilometres to metres, then change the metres to centimetres.

measure
time60 seconds in a minute60 minutes in an hour24 hours in a day
calendar7 days in a weeksee below for days in a month12 months in a yearsee below for days in a year
length10mm in a centimetre (cm)100cm in a metre (m)1000m in a kilometre (km)
area100mm2 in a square centimetre10 000cm2 in a square metre1 000 000m2 in a square kilometre
volume1 000mm3 in 1cm31 000 000cm3 in a cubic metre
capacity1000ml in a litre
mass1000g in a kilogram (kg)1000kg in a tonne

Special notes on the calendar: in a Leap Year (2016, 2020, 2024, 2028), the year is 366 days long and February has 29 days. All other years are 365 days long and February is 28 days long. April, June, September and November are each 30 days long: the remaining months are each 31 days long.

Examples

1. How many centimetres are in 4.25km?

Answer: 425,000

Change 4.25km to metres by multiplying by 1000 (1000m in a km) = 4.25 x 1000 = 4250m.

Change 4250m to cm by multiplying by 100 (100cm in a m) = 4250 x 100 = 425 000cm.

2. How many complete hours are there in 1 000 000 seconds?

Answer: 277 days

Divide 1 000 000 by 60 to get minutes (60 minutes in an hour) = 16.66666 minutes.

Divide 16.6666 by 60 to get hours (60 minutes in an hour) = 277.777 hours.

The question asked for complete hours, so 277 hours.