8th Class
Mathematics
Direct and Inverse Proportions
Question Bank
Direct and Inverse Proportions
question_answer
In 15 days, the earth picks up \[1.2\times {{10}^{8}}\text{kg}\] of dust from the atmosphere. In how many days it will pick up \[4.8\times {{10}^{8}}\text{ kg}\]of dust?
A) 50
B) 40
C) 60
D) 100
Correct Answer:
C
Solution :
Number of days
15
x
Weight of dust (in kg)
\[1.2\times {{10}^{8}}\]
\[4.8\times {{10}^{8}}\]
More the dust, more the number of days it will take to pick it up. So, it is a case of direct proportion. \[\therefore x=\frac{15}{1.2\times {{10}^{8}}}\times 4.8\times {{10}^{8}}days\] \[\Rightarrow x=\frac{15\times 4.8}{1.2}=60days\]