102
Solving problems on the number ray
Textbook: Part 3, lesson 102, pp. 104–106
GoalSolve problems with the number ray: movement at a steady speed and logic problems about order.
New words
running · yugurisharrangement · joylashuvorder · tartibform an equation · tenglama tuzish
Explanation
The number ray helps with movement and order problems. If a child runs 3 m per second, in 2 seconds she runs 6 m, in 3 seconds 9 m: distance = 3 × number of seconds. To find the time for a given distance we divide: 27 : 3 = 9 seconds. In order problems (“A is left of B, B is left of C”) we draw a ray and place each person. From a picture we can form an equation: whole = sum of parts.
Worked examples
Umida runs 2 m per second. In 5 s she runs 5 × 2 = 10 m and she covers 22 m in 22 : 2 = 11 s.
Three children sit on a bench: Sardor is left of Dilnoza and Dilnoza is left of Zarina. From left to right: Sardor, Dilnoza, Zarina.
Class activity
“Order on the bench”: 4 children sit on a bench. Classmates give clues like “Anvar is left of Bahodir” and “Bahodir is left of Dildora”, and the rest find the order.
Practice
1
A child runs 3 m per second. How many metres does she run in 7 seconds?
21
2
A child runs 3 m per second. How long does it take to run 27 m? (seconds)
9
3
A box held x apples. 18 apples were added and there were 45. Find x.
27
4
Point A(7) moves 2 units right, 2 units right again and then 3 units left. What coordinate does it stop at?
8
5
The plane tree is taller than the poplar and the poplar is taller than the spruce. Which tree is the shortest?
The spruce