Page 163 - NUMINO Challenge_C2
P. 163
Answer
Key
Communication 2 The sum of the distances walked in 2 minutes is
13 Distance and Speed p.112~p.113 equal to the length of the track, which is 600 m.
When they are walking in the same direction,
Example 90 90, 900 Jean needs to walk one more round around the
track to meet Kelly. The sum of the distances
Example 1,350 1,350, 9 walked in 6 minutes is 600 3 1800 m. Jean
walks 600 m more than Kelly, then Kelly walked
(1800 600) 2 600 m, and Jean walked 1200
m. Since Jean walks 1200 m in 6 minutes, she
walks 1200 6 200 m in 1 minute.
TryItAgain The distance that the train needs to travel to Type 13-2 Crossing Bridges p.116~p.117
completely cross the bridge is 8,320 80
8,400 m. 1 The train takes 25 15 10 seconds to travel
Since the train is traveling at 700 m per 250 m, which is the difference between the
minute, it will take 8,400 700 12 minutes lengths of the two bridges.
to completely cross the bridge.
2 Since it takes 10 seconds to travel 250 m, then it
Type 13-1 Catching Up p.114~p.115 travels 250 10 25 m per second. Therefore, it
travels 25 15 375 m in 15 seconds.
1 The sum of the distances walked per minute is
80 60 140 m; therefore, they walked 3 When the train completely crosses the bridge,
140 10 1,400 m in 10 minutes. Therefore, the the distance it travels is (Length of the bridge)
length of the track is 1,400 m. (Length of the train), which is 350 (Length of
the train) 375 m. Therefore, the length of the
2 Chris walks faster than Megan; therefore, she train is 25 m.
cannot catch up with him. Therefore, the only
time they meet with each other is when Chris 4 The train travels 25 m per second, so in 20
catches up with Megan after he finishes one seconds, it moves 25 20 500 m. This is equal
round. to the distance that the train travels when it
completely crosses the bridge, which is (Length
3 They will meet when Chris walks 1,400 m more of the tunnel) 70 m. Therefore, the length of
than Megan. Chris walks 20 m per minute faster the tunnel is 500 70 430 m.
than Megan. Therefore, it will take 1,400 20
70 minutes for them to meet.
Problem solving Problem solving
1 Joe cycles 150 m in 10 seconds and Grace runs 1 The length of the train remains the same, and
30 6 5 m per second. Since the distance the train travels 24 m in 3 seconds. Therefore,
traveled by the two people in 15 seconds is the train travels 24 3 8 m in 1 second.
(15 5) 15 300 m, the perimeter of the pond
is (15 5) 15 300 m.
NUMINO Challenge C2
Key
Communication 2 The sum of the distances walked in 2 minutes is
13 Distance and Speed p.112~p.113 equal to the length of the track, which is 600 m.
When they are walking in the same direction,
Example 90 90, 900 Jean needs to walk one more round around the
track to meet Kelly. The sum of the distances
Example 1,350 1,350, 9 walked in 6 minutes is 600 3 1800 m. Jean
walks 600 m more than Kelly, then Kelly walked
(1800 600) 2 600 m, and Jean walked 1200
m. Since Jean walks 1200 m in 6 minutes, she
walks 1200 6 200 m in 1 minute.
TryItAgain The distance that the train needs to travel to Type 13-2 Crossing Bridges p.116~p.117
completely cross the bridge is 8,320 80
8,400 m. 1 The train takes 25 15 10 seconds to travel
Since the train is traveling at 700 m per 250 m, which is the difference between the
minute, it will take 8,400 700 12 minutes lengths of the two bridges.
to completely cross the bridge.
2 Since it takes 10 seconds to travel 250 m, then it
Type 13-1 Catching Up p.114~p.115 travels 250 10 25 m per second. Therefore, it
travels 25 15 375 m in 15 seconds.
1 The sum of the distances walked per minute is
80 60 140 m; therefore, they walked 3 When the train completely crosses the bridge,
140 10 1,400 m in 10 minutes. Therefore, the the distance it travels is (Length of the bridge)
length of the track is 1,400 m. (Length of the train), which is 350 (Length of
the train) 375 m. Therefore, the length of the
2 Chris walks faster than Megan; therefore, she train is 25 m.
cannot catch up with him. Therefore, the only
time they meet with each other is when Chris 4 The train travels 25 m per second, so in 20
catches up with Megan after he finishes one seconds, it moves 25 20 500 m. This is equal
round. to the distance that the train travels when it
completely crosses the bridge, which is (Length
3 They will meet when Chris walks 1,400 m more of the tunnel) 70 m. Therefore, the length of
than Megan. Chris walks 20 m per minute faster the tunnel is 500 70 430 m.
than Megan. Therefore, it will take 1,400 20
70 minutes for them to meet.
Problem solving Problem solving
1 Joe cycles 150 m in 10 seconds and Grace runs 1 The length of the train remains the same, and
30 6 5 m per second. Since the distance the train travels 24 m in 3 seconds. Therefore,
traveled by the two people in 15 seconds is the train travels 24 3 8 m in 1 second.
(15 5) 15 300 m, the perimeter of the pond
is (15 5) 15 300 m.
NUMINO Challenge C2
