Units of time

1 min (minute) = 60 s (seconds)
1 h (hour) = 60 min

1.5 h = $1{1/2}$h = 1 h 30 min
1 h = 60 × 60 s= 3600 s

Units of time

1 min (minute) = 60 s (seconds)
1 h (hour) = 60 min

1.5 h = $1{1/2}$h = 1 h 30 min
1 h = 60 × 60 s= 3600 s

Units of time

1 min (minute) = 60 s (seconds)
1 h (hour) = 60 min

1.5 h = $1{1/2}$h = 1 h 30 min
1 h = 60 × 60 s= 3600 s

day = 24 h
week = 7 days (Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday)

month = from 28 to 31 days

Month	Number of days
January	31
February	28 or 29
March	31
April	30
May	31
June	30
July	31
August	31
September	30
October	31
November	30
December	31

year = 12 months = 365 days = 52 weeks 1 day
leap year = 12 months = 366 days = 52 weeks 2 days

A leap year is a year in which an extra day is added to the calendar in order to synchronize it with the seasons. In leap years, February 29th is added as leap day, which doesn't exist in a normal year (February has normally 28 days). A leap year occurs every 4 years - the year has to be evenly divided by 4 (2004, 2008, 2012), but not by 100 (1800, 1900, 2100). However, if it is divisible by 400, it's again a leap year (2000).

Metric units of length

m... meter
dm... decimeter
cm... centimeter

1 m = 100 cm = 10 dm
1 dm = 10 cm

Metric units of length

1 cm (centimeter) = 10 mm (milimeter)
1 dm (decimeter) = 10 cm
1 m (meter) = 100 cm = 10 dm
1 km (kilometer)= 1000 m

Metric units of length

1 cm (centimeter) = 10 mm (milimeter)
1 dm (decimeter) = 10 cm
1 m (meter) = 100 cm = 10 dm
1 km (kilometer)= 1000 m

Metric units of length

1 cm (centimeter) = 10 mm (milimeter)
1 dm (decimeter) = 10 cm
1 m (meter) = 100 cm = 10 dm
1 km (kilometer)= 1000 m

Customary units of length

1 inch (in) ≅ 2.54 centimeters (cm)
1 foot (ft or ′) = 12 in ≅ 30.48 cm
1 yard (yd) = 3 ft = 36 in ≅ 0.91 meter (m)
1 mile (mi)= 1760 yd ≅ 1.6 kilometer (km)

Metric units of area

1 cm² = 10 mm × 10 mm = 100 mm²
1 dm² = 10 cm × 10 cm = 100 cm²

1 m² = 10 dm × 10 dm = 100 dm² = = 10000 cm²
1 km² = 1000 m × 1000 m = 1000000 m²

Metric units of mass

1 g (gram) = 1000 mg (milligram)
1 kg (kilogram)= 1000 g
1 t (ton) = 1000 kg

1 dkg (dekagram) =10 g
1 kg (kilogram)= 1000 g = 100 dkg

Customary units of mass

1 pound (lb) = 16 ounces (oz) ≅ 0.45 kilogram (kg)
1 oz ≅ 28 grams (g)
1.5 lb = 16 + 8 = 24 oz
$1/2$ lb = 8 oz

l (L)... liter
hl (hL)... hectoliter

1 hl =100 l

l (L)... liter
ml (mL)... mililiter

1 l =1000 ml

Velocity unit conversion

Velocity is measured as distance traveled per certain unit of time, e.g. if car drives 40 km/h, that means that a car drives 40 km every hour (40 km in one hour, 80 in two hours, 120 in three hours. etc.). The American equivalent is mph (miles per hour). Since this is a combination of units (distance divided by time), when recalculating to different units of velocity we need to pay attention to both units (time and distance), and determine how to change them.

If we are moving 2 m/s, it means that every second we travel 2 meters. How many meters will we travel in one hour? One hour has 3600 seconds.

In one hour we will travel 7200 m. And how many kilometers will we move in 1 hour? We know that 1 km is equal to 1000 m.

If a car is moving 90 km/h, how many meters per second will it drive? In this case we have to multiply 90 by 1000 to calculate the meters (90 km=90000 m). At the same time we have to divide the value by 3600 since one hour has 3600 seconds:

So the car is driving 25 m/s. But what is his speed in km/min? As we know, 1 hour has 60 minutes. It means that in one minute it will drive: