Page 165 - NUMINO Challenge_D2

Answer
Key

Communication 3 The amount of work Tom and John did in 10

days was 1 10 5 . Therefore, the amount
12 6

of work left is 1 .
6
13 Work and Its Efficiency p.112~p.113

4 The remaining amount of work is 1 . Since the
6
11 1
Example 30, 30 , 60, 60 amount of work John can finish in a day is 30 , if

1 , 1 , 1 1 , 20 John works alone, it will take 1 1 5 days
30 60 20 20 6 30

for him to finish the work.

TryItAgain Let 1 represents the total amount of work. Therefore, it will take 10 5 15 days to finish

The amount of work A can do in 1 hour is the entire work.

1 10 1 , and the amount of work B can
10
1
do in 1 hour is 1 10 40 . If A and B work

together, the amount of work A and B can Problem solving

do is1110 1 1 . Therefore, it will take
1 8 40 8 fix the road.
8 1 Let 1 represents the amount of work one person
hours to
can finish in a day. Then the amount of work 6

people can finish in 18 days is 6 18 108.

Example 48, 60 60, 48, 3 Let represents the days only 3 people worked.

Since 4 6 3 108, 28 days.

TryItAgain Let 1 represents the amount of grass the cow 2 Let 1 represents the entire work. Then the amount
eats a day. To maintain a constant amount of
grass, 3 cows should be raised on the ranch. of work a boy can finish in a day is 1 , and the
amount of work a girl can finish in 3
1
a day is 5 .

Type 13-1 Application of Work Efficiency p.114~p.115 The amount of work six men can do a day is

1 6 5 10.
3

1 Let 1 represent the amount of work. Since the amount of work 3 boys and 3 girls can

The amount of work Tom can finish in a day is finish in a day is 1 3 1 3 8 , then it will
3 5 5
1 20 1 , and the amount of work John can 8 1
finish in 20 take 10 5 6 4 days to finish the entire
1
a day is 1 30 30 . work. Therefore, it will take 7 days to finish the

2 If Tom and John work together, the amount of work.

work they can finish in a day is 1 1 1 .
20 30 12

NUMINO Challenge D2