# Units of measurement

Estimate the length (mm, cm, m, km)

## Metric units of length

Millimeters (mm):

We can use millimeters to measure things like the width of a small button, the length of an insect, or the size of tiny beads on a necklace.

Centimeters (1 cm=10 mm):

Centimeters are handy for measuring things that are a bit larger. For example, you can measure the length of your crayon, the width of a small toy car, or the height of your favorite action figure.

Meters (1 m = 100 cm):

Meters are great for bigger measurements. You can use meters to measure how tall you are, the length of your classroom, or the width of a soccer field.

Kilometers (1 km = 1000 m):

Kilometers are used for really long distances. You might use kilometers to measure the distance between your home and school, the length of a hiking trail, or the distance between cities on a map.

So, millimeters are for tiny things, centimeters for small things, meters for medium-sized things, and kilometers for really big things!

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Estimate the mass (g, kg, t)

## Metric units of mass

Grams (g):

Grams are used to measure the weight of small and light objects. For example, you can measure the mass of a small toy, a pencil, or your favorite fruit using grams.

Kilograms (1 kg = 1000 g):

Kilograms are a bit larger and are great for measuring the weight of things that are heavier. You can use kilograms to measure the mass of your backpack, a watermelon, or even your pet cat or dog.

Metric Tons (t = 1000 kg):

Metric tons are the largest unit in this series and are used for really heavy things. You might use metric tons to measure the weight of a car, the amount of food a big truck can carry, or the weight of a large animal like an elephant.

So, grams are for light things, kilograms for heavier objects, and metric tons for really, really heavy stuff!

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Estimate the length (in, ft, yd)

## Units of length

Inches (in):

Inches are used to measure small lengths, like the size of a paperclip, the length of a small toy car, or the width of a bookmark. It's like counting tiny steps when measuring.

Feet (1 ft = 12 in):

Feet are a bit bigger and great for measuring longer things. You can use feet to measure the length of your bed, the height of a kitchen counter, or how far you can jump. It's like taking bigger steps when measuring.

Yards (1 yd=3 ft):

Yards are even longer and are used for measuring larger distances. For example, you can use yards to measure the length of a football field, the width of a driveway, or the distance you run during a race. It's like taking really big steps when measuring.

So, inches are for small lengths, feet for longer things, and yards for even bigger distances!

The unit feet has an interesting origin. Back in ancient times, people used to measure length based on body parts, like the length of their foot. One foot was approximately the length of an average adult foot. Over time, this informal practice evolved into a standardized unit of measurement. Today, one foot is equal to 12 inches, and it helps us measure and understand lengths in a way that traces back to the way people measured things many, many years ago. So, when we talk about feet, we're essentially referring to a unit based on the length of a foot!

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Estimate the mass (lb, oz)

## Units of mass

Ounces (oz):

Ounces are used to measure the mass of small things. You can use ounces to measure the mass of a small toy, a piece of candy, or the weight of your favorite snack. It helps you understand how heavy or light things are.

Pounds (lb):

Pounds are larger than ounces and are great for measuring the weight of bigger things. For example, you can use pounds to measure the weight of your pet hamster, a backpack, or a bag of flour in the kitchen. So, ounces are for small, light things, and pounds are for heavier, larger objects. It's like having different tools for measuring the weight of things, depending on whether they are tiny or bigger.

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Convert units of time (seconds and minutes)

## 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

Convert units of time (seconds, minutes and hours)

## 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

Convert units of time (months)

## 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).

Convert metric units of length (cm, dm, m)

## Metric units of length

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

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

Convert metric units of length (easy)

## 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

Convert metric units of length (medium)

## 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

Convert metric units of length (difficult)

## 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

Convert and compare US units of length (inches, feet, yards)

## 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)

Convert metric units of area

## 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

Convert and compare units of mass (kg and g)

## 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

Convert and compare US units of mass (ounces and pounds)

## 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

Convert and compare units of volume (l and hl)

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

1 hl =100 l

Convert and compare units of volume (l and ml)

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

1 l =1000 ml

Metric units of measurement as decimals (easy)

Convert metric units of speed/velocity

## 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.

\$\$2;m/s=\$\$
\$\$=2×3600=7200;m/s\$\$

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.

\$\$ 7200;m/s=7.2;km/s \$\$

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:

\$\$90;km/h={90000;m}/{3600;s}=25;m/s\$\$

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:

\$\$90;km/h=\$\$
\$\$={90;km}/{60;min}=1.5;km/min\$\$