NCERT Class 8 Mathematics Solutions: Chapter 13 – Direct and Inverse Proportions Exercise 13.1 Part 3
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1. Rashmi has a road map with a scale of representing. She drives on a road for . What would be her distance covered in the map?
Answer:
Consider distance covered in the map be .
Actual distance (in km) | ||
Distance covered in map (in cm) |
Actual distance and distance covered in the map are in direct proportion.
So, the distance covered in the map is .
2. A high vertical pole casts a shadow long. Find at the same time
(i) The length of the shadow cast by another pole high
(ii) The height of a pole which casts a shadow long.
Answer:
Height of the pole and length of the shadow are in direct proportion.
And
(i) Consider,
The length of the shadow of another pole be .
Height of pole (in cm) | ||
Length of shadow (in cm) |
So, the length of the shadow of another pole is .
(ii) Consider,
The height of the people be .
Height of pole (in cm) | ||
Length of shadow (in cm) |
So, the length of the shadow of another pole is .
3. A loaded truck travels 14 km in 25 minutes. If the speed remains the same, how far can it travel in 5 hours?
Answer:
Consider,
Distance covered in 5 hours be x km
∵1 hour=60 minutes
∵5 hours=5×60
=300 minutes
Distance (in km) 14 x
Time (in minutes) 25 300
Distance covered and time in direct proportion.
→14/25=x/300
→x×25=14×300
→x=(14×300)/25
→168 km
So, the distance covered in 5 hours is 168 km.