Question

20 men can build a wall in nine days, then how long would it take 12 men to build
the same wall?​

Answer 1

Step-by-step explanation:

20 m×9d=12m×?days

?days=180d/12

=15 days

Answer 2

Given:

• 20 men can build a wall in nine days

To Find:

• The number if days 12 men will take to build the wall

Solution:

→ here, as per the second case the number of workers decreased so, the number of days will increase accordingly

• hence we can say the the following ratios are inversely proportional to each other.

So, the ratios are :

• ➪ $\bf\pink{ 20 : 9 }$

• ➪ $\bf\pink{ 12 : x }$

Since,

• it is inverse variation we apply straight multiplication

$\purple{ \underline{ \mathfrak{Let \: us \: solve \: \dag}}}$

${ : \implies} \tt \: 20 \times 9 = 12 \times x \\ \\ \\ { : \implies} \tt x = \frac{20 \times \cancel 9}{ \cancel{12}} \: \: \: \: \: \: \: \: \: \\ \\ \\ { : \implies} \tt \: x \: = \frac{ \cancel{20} \times 3}{ \cancel4} \: \: \: \: \: \: \\ \\ \\ { : \implies} \tt \: x \: = 5 \times 3 \: \: \: \: \: \: \: \: \: \: \\ \\ \\ { : \implies}{ \underline { \boxed{ \bf{x = 15}}} \bigstar} \: \: \: \: \: \: \: \: \:$

therefore,

• 12 men will take 15 days to complete the work

More to know:

What is proportion?

• A proportion is an equation that says that two or more ratios are equal.

Types of proportion:

• Direct proportion
• Inverse proportion

Two variables are said to be in proportion if the change in one can be predicted from a change in the other.

Synonyms of proportion:

• comparison.
• share.
• distribution
• arrangement
• balance

$\sf{happy \: learning}$