Question

If an amount of food last for 20 days for 120 men, how long will it last for 80 men at the same rate

20 days

30 days

35 days

25 days

​

Answer 1

Answer:

480

Step-by-step explanation:

20 multiplied by 6 is 120

so 80 multiplied by 6 is 480

Answer 2

Given:

✰ An amount of food last for 20 days for 120 men

✰ An amount of food lasts when there are 80 men.

To find:

✠ Number of days for how long the food will last when there are 80 men.

Solution:

To understand this question, first we will see what is direct and indirect variation.

Direct variation

⚘ Two quantities are said to have direct variation, if the increase in one quantity causes an increase in the other quantity and decrease in one quantity causes a decrease in other quantity.

Indirect variation

⚘ Two quantities said to be very inversely, if an increase in one quantity decreases the other quantity and decrease in one quantity increases the other quantity.

❖ Now, let's see the question and understand the concept here. As there are more men ( 120 men, increase in quantity ), there will be less days ( 20 days, decrease in quantity ). Now, when there are less men ( 80 men, decrease in quantity ), there will be more days ( increase in quantity ). Therefore, It is a Indirect variation or inverse variation.

✭ In inverse variation, x₁y₁ = x₂y₂✭

Here,

• x₁ = 20
• y₁ = 120
• x₂ = x
• y₂ = 80

Let for 80 men food will last for x days.

Now,

➤ 20 × 120 = x × 80

➤ x = ( 20 × 120 )/80

➤ x = 2400/80

➤ x = 30

∴ An amount of food last for 30 days for 80 men

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