NCERT Solutions for Class 8th Mathematics
Chapter 13. Direct and Inverse Proportions
Q1. Following are the car parking charges near a railway station upto
4 hours Rs 60
8 hours Rs 100
12 hours Rs 140
24 hours Rs 180
Check if the parking charges are in direct proportion to the parking time.
Q2. A mixture of paint is prepared by mixing 1 part of red pigments with 8 parts of base. In the following table, find the parts of base that need to be added.
Q3. In Question 2 above, if 1 part of a red pigment requires 75 mL of base, how much red pigment should we mix with 1800 mL of base?
Q4. A machine in a soft drink factory fills 840 bottles in six hours. How many bottles will it fill in five hours?
Q5. A photograph of a bacteria enlarged 50,000 times attains a length of 5 cm as shown in the diagram. What is the actual length of the bacteria? If the photograph is enlarged 20,000 times only, what would be its enlarged length?
Q6. In a model of a ship, the mast is 9 cm high, while the mast of the actual ship is 12 m high. If the length of the ship is 28 m, how long is the model ship?
Therefore the length of model ship is 21 cm.
Q7. Suppose 2 kg of sugar contains 9 × 106 crystals.
How many sugar crystals are there in
(i) 5 kg of sugar?
(ii) 1.2 kg of sugar?
Q8. Rashmi has a road map with a scale of 1 cm representing 18 km. She drives on a road for 72 km. What would be her distance covered in the map?
Q9. A 5 m 60 cm high vertical pole casts a shadow 3 m 20 cm long. Find at the same time
(i) The length of the shadow cast by another pole 10 m 50 cm high
(ii) The height of a pole which casts a shadow 5m long.
Q10. A loaded truck travels 14 km in 25 minutes. If the speed remains the same, how far can it travel in 5 hours?