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Solving math problems for grade 5 pages 72, 73 VBT set 2, Concentrated Exercise, Exercise 138 provides detailed solutions for exercises 1, 2, 3 closely aligned with the content to help students easily visualize the process, compare their steps with theirs. At the same time, students can grasp the best way to solve problems related to speed, distance, and time.
Solving math problems for grade 5 pages 72, 73 VBT set 2, Concentrated Exercise, Exercise 138
1. Solve exercise 1 - Math workbook grade 5 set 2 page 72
Problem statement:
Fill in the blank with the appropriate measurement:
Solution Method:
Apply the following formulas:
v = s : t ; s = v x t ; t = s : v
where s represents distance, v represents speed, and t represents time.
Answer
+) Conversion: 1 hour 20 minutes = 4/3 hours
The distance in the first blank is:
42 x 4/3 = 56 (km)
+) The speed in the second blank is:
95 : 2.5 = 38 (km/hour)
+) The time in the third blank is:
84.7 : 24.2 = 3.5 (hours)
+) Change: 1 minute 20 seconds = 80 seconds
The speed in the fourth blank is:
The result is 400 divided by 80 equals 5 (m/s)
We have the following table of results:
2. Solve Exercise 2 - Math workbook Grade 5 Volume 2 Page 73
Problem:
A motorcycle travels from C to B at a speed of 36 km/hour. At the same time, a car travels from A, which is 45 km away from C, chasing the motorcycle at a speed of 51 km/hour (see the diagram). Calculate the time it takes for the car to catch up to the motorcycle.
Solution:
- Find the speed difference between the two vehicles.
- Find the time it takes for the car to catch up to the motorcycle = distance AB (which is the initial distance between the two vehicles when both start) : speed difference between the two vehicles.
Answer:
The speed difference between the car and the motorcycle is :
51 - 36 = 15 (km/hour)
The time it takes for the car to catch up to the motorcycle is :
45 : 15 = 3 (hours)
Answer: 3 hours.
3. Solve problem 3 - Math workbook grade 5 exercise 2 page 73
Problem:
The speed of the water current is 18 m/minute. A person swims downstream a river segment 800m long in 8 minutes. How long does it take for the person to swim upstream along that river segment?
Guide: The downstream swimming speed equals the sum of the still water swimming speed and the water current speed. The upstream swimming speed equals the difference between the still water swimming speed and the water current speed.
Solution Method
- Find the downstream swimming speed = river segment length : time for downstream swimming.
Find the actual swimming speed of the person = downstream swimming speed - water current speed.
Find the swimming speed upstream = actual speed of the person + water current speed.
Find the time for upstream swimming = river segment length : upstream swimming speed.
Answer
The downstream swimming speed of a person is:
800 : 8 = 100 (m/minute)
The actual swimming speed of the person is:
100 - 18 = 82 (m/minute)
The upstream swimming speed of that person is:
82 - 18 = 64 (m/minute)
The time to swim upstream the river section is:
800 : 64 = 12.5 minutes
12.5 minutes = 12 minutes 30 seconds
Answer: 12 minutes 30 seconds
You are watching the guidance for solving math problems for grade 5, pages 72 and 73 of Exercise 2 workbook. You can review the guidance on solving math problems for grade 5, pages 71 and 72 of Exercise 2 to understand more about the lesson.
Wishing you all the best in learning mathematics.
