20. Claude spent 14 hour going to school riding in a jeep and took 72 hour returning
ne from school by riding a tricycle. How many hours did he spend travelling in all?
a. 12.
b. 2/3
c. 3
d. 4/5
ne from school by riding a tricycle. How many hours did he spend travelling in all?
a. 12.
b. 2/3
c. 3
d. 4/5
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Answer:
I have 3 solutions as follows.
Using a single variable.
Let x be the number of students in question. The number of students using tricycles is 16−x. The total number of wheels is the sum of the total number of bicycles times 2 and the total number of tricycles times 3.
2×x+3×(16−x)=38
The solution is x=10.
Using 2 variables.
Let x and y be the number of students using bicycles and tricycles, respectively. It implies that
x+y2x+3y=16=38
The solution is x=10 and y=6.
Using multiples
The multiples of 2 are 2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,…
The multiples of 3 are 3,6,9,12,15,18,21,24,27,30,33,36,…
The possible wheel combinations with format (#bicycle wheels,#tricycle wheels):
(32,6) but there are 18 students
(26,12) but there are 17 students
(20,18) there are 16 students
(14,24) there are 15 students
(8,30) there are 14 students
(2,36) there are 13 students
Thus the correct combination is 10 bicycles and 6 tricycles.