17
Adding multi-digit numbers (practice)
Textbook: Part 1, lesson 17, pp. 52–54
GoalPractise adding multi-digit numbers; letter expressions and the hectare.
New words
letter expression · harfiy ifodahectare · gektar (ga)area of land · maydonaddend · qo‘shiluvchi
Explanation
When adding, the places must be lined up correctly. If an amount is unknown we write a letter for it: 42 × n + 4 × m is a letter expression. Putting in values for the letters gives the value of the expression. Land area is measured in hectares: 1 ha = 10 000 m².
Worked examples
If n = 3 and m = 2, then 42 × n + 4 × m = 42 × 3 + 4 × 2 = 126 + 8 = 134.
5 318 + 8 764 = 14 082; 3 ha = 3 × 10 000 = 30 000 m².
Class activity
“Buses and taxis”: each group writes an expression for n buses (42 seats) and m taxis (4 seats). The teacher gives values of n and m and groups work out the total passengers.
Practice
1
5 318 + 8 764 = ?
14082
2
906 428 + 85 972 = ?
992400
3
How many square metres are in 4 hectares?
40000
4
A park has a benches for 3 people and b benches for 5 people. If a = 15 and b = 20, how many people can sit in total?
145
5
Find the value of 42 × n + 4 × m when n = 4 and m = 6.
192