Length units, surface area and the calendar · Grade 4
In Length units, surface area and the calendar (Grade 4) you practise 3 skills: Length units · Surface area of a box · The calendar. The units of length are the kilometre (km), the metre (m), the decimetre (dm), the centimetre (cm) and the millimetre (mm). A kilometre is 1,000 metres; a metre is 10 decimetres or 100 centimetres; a decimetre is 10 centimetres; and a centimetre is 10 millimetres.
To change from a larger unit to a smaller one, multiply: 3 metres are 3 × 100 = 300 centimetres. To compare lengths written in different units, write them both in the same unit. A cuboid has six rectangular faces, and each face is equal to the one opposite it. Its surface area is the sum of the areas of all six faces: 2 × (length × width) + 2 × (length × height) + 2 × (width × height). A cube has six equal square faces. A common year has 365 days and 12 months. A week has 7 days, so 45 days are 6 weeks and 3 more days. To count the days from a date in one month to the same date in a later month, add up the days in the months that pass.
Tip: To find the surface area without missing a face, unfold the cuboid in your mind: three pairs of equal rectangles.
What you learn
Length units
For example: How many metres are there in 9 km?
Answer and solution
The answer: 9000 m
There are 1,000 metres in 1 km, so: 9 × 1,000 = 9,000
Surface area of a box
For example:
What is the surface area of the cube, in cm²? The edges are in centimetres.Answer and solution
The answer: 600 cm²
The area of one face: 10 × 10 = 100 . There are 6 faces: 6 × 100 = 600
The calendar
For example: How many days are there in June in a common year?
Answer and solution
The answer: 30
June has 30 days.
The exercises are made by rules and the answers are worked out in code, so there are new exercises every time. The topic follows the new Israeli elementary programme (2023).