Page 166 - NUMINO Challenge_D2
P. 166
Type 13 -2 Filling the Bathtub p.116~p.117 Creative Thinking p.118~p.119
1 90 mL of water runs down from faucet A every 1 Let 1 represent the entire amount of work. In
2 seconds, therefore 90 2 45 mL of water runs 1
down every second. 190 mL of water runs down one day, A can do 4 of the work, B can do
from faucet B every 5 seconds, therefore
190 5 38 mL of water runs down every second. 1 of work, and C can do 1 of the work.
6 12
2 The amount of water that leaks out of the
bathtub every second is 9 3 3 mL. If A, B, and C work together, the amount of
3 Every second, an amount of 45 mL of water runs work they can finish in one day is
down from faucet A and an amount of 38 mL
runs down from faucet B. Since an amount of 1 11 6 1 .
3 mL of water leaks out every second, the 4 6 12 12 2
amount of water that fills up the bathtub in one
second is 45 38 3 80 mL. Therefore, since 1 represents the entire amount
4 The bathtub is filled with 80 mL of water every of work, it will take 1 1 2 days for three
second. Since 20 L 20,000 mL, it will take 2
20,000 80 250 seconds to fill a 20-L bathtub.
people to finish the work.
Problem solving 2 Let 1 represent the amount of grass a cow eats
in a day. Then the amount of grass 5 cows eat in
4 days is 5 4 20, and the amount of grass
3 cows eat in 8 days is 3 8 24.
The difference between the amount of grass
eaten in 8 days and 4 days is equal to the
amount of grass that grows in 4 days, therefore
the amount of grass that grows in a day is
(24 20) 4 1. Therefore, 1 cow should be
raised the farm to maintain a constant amount of
grass.
1 Since 70 mL of hot water runs down for one 3 Let 1 represent the amount of work a worker can
minute and 150 3 50 mL of cold water runs do in an hour. Then the amount of work 10
down for one minute, the amount of water that workers can do in 1 hour is 1 10 10, and the
fills the container in one minute is 70 50 120 amount of work 10 workers can do in 10 hours is
mL. Since 6 L 6,000 mL, it will take 10 10 100 (the entire work). Since the amount
6,000 120 50 minutes to fill the 6-L container. of work 5 workers can do in 4 hours is 5 4 20,
the remaining amount of work is 100 20 80.
2 Let 1 represent the amount of water filled in the Since 3 more workers came later to finish the
remaining work, the 8 workers need to work
bowl. Since the chick drinks 1 of the entire 80 8 10 more hours.
30
amount of water in 1 minute, it drinks
6 1 of the entire amount of water in 6 4 When only faucet A was turned on for 10
30 5
minutes, the amount of water that filled the
minutes. container was 170 110 80 L, therefore an
amount of 60 10 6 L ran down faucet A in
Therefore, the amount of water left by the chick one minute. Since the amount of water that ran
down when only faucet A was turned on was
is 1 1 4 . Since the dog can drink 200 110 90 L, it will take 90 6 15 minutes
5 5 to fill the container.
the entire amount of water in 1 minute, it will
take the dog 4 1 16 minutes to drink
5 20
the remaining water.
Answer Key
1 90 mL of water runs down from faucet A every 1 Let 1 represent the entire amount of work. In
2 seconds, therefore 90 2 45 mL of water runs 1
down every second. 190 mL of water runs down one day, A can do 4 of the work, B can do
from faucet B every 5 seconds, therefore
190 5 38 mL of water runs down every second. 1 of work, and C can do 1 of the work.
6 12
2 The amount of water that leaks out of the
bathtub every second is 9 3 3 mL. If A, B, and C work together, the amount of
3 Every second, an amount of 45 mL of water runs work they can finish in one day is
down from faucet A and an amount of 38 mL
runs down from faucet B. Since an amount of 1 11 6 1 .
3 mL of water leaks out every second, the 4 6 12 12 2
amount of water that fills up the bathtub in one
second is 45 38 3 80 mL. Therefore, since 1 represents the entire amount
4 The bathtub is filled with 80 mL of water every of work, it will take 1 1 2 days for three
second. Since 20 L 20,000 mL, it will take 2
20,000 80 250 seconds to fill a 20-L bathtub.
people to finish the work.
Problem solving 2 Let 1 represent the amount of grass a cow eats
in a day. Then the amount of grass 5 cows eat in
4 days is 5 4 20, and the amount of grass
3 cows eat in 8 days is 3 8 24.
The difference between the amount of grass
eaten in 8 days and 4 days is equal to the
amount of grass that grows in 4 days, therefore
the amount of grass that grows in a day is
(24 20) 4 1. Therefore, 1 cow should be
raised the farm to maintain a constant amount of
grass.
1 Since 70 mL of hot water runs down for one 3 Let 1 represent the amount of work a worker can
minute and 150 3 50 mL of cold water runs do in an hour. Then the amount of work 10
down for one minute, the amount of water that workers can do in 1 hour is 1 10 10, and the
fills the container in one minute is 70 50 120 amount of work 10 workers can do in 10 hours is
mL. Since 6 L 6,000 mL, it will take 10 10 100 (the entire work). Since the amount
6,000 120 50 minutes to fill the 6-L container. of work 5 workers can do in 4 hours is 5 4 20,
the remaining amount of work is 100 20 80.
2 Let 1 represent the amount of water filled in the Since 3 more workers came later to finish the
remaining work, the 8 workers need to work
bowl. Since the chick drinks 1 of the entire 80 8 10 more hours.
30
amount of water in 1 minute, it drinks
6 1 of the entire amount of water in 6 4 When only faucet A was turned on for 10
30 5
minutes, the amount of water that filled the
minutes. container was 170 110 80 L, therefore an
amount of 60 10 6 L ran down faucet A in
Therefore, the amount of water left by the chick one minute. Since the amount of water that ran
down when only faucet A was turned on was
is 1 1 4 . Since the dog can drink 200 110 90 L, it will take 90 6 15 minutes
5 5 to fill the container.
the entire amount of water in 1 minute, it will
take the dog 4 1 16 minutes to drink
5 20
the remaining water.
Answer Key
