What should come in place of the question mark (?) in the following number series?

# Category: Mathematics

## National Mathematics Day 2022: Date, History, Significance, More

National Mathematics Day 2022: Date, History, Significance, More

## If a : b = 20:5 then find out the value of (13a-9b): (11a-7b)?

If a : b = 20:5 then find out the value of (13a-9b): (11a-7b)?

## A can paint a house in 55 days and B can do it 66 days. Along with C, they did the job in 12 days only. Then, C alone can do the job in how many days?

A can paint a house in 55 days and B can do it 66 days. Along with C, they did the job in 12 days only. Then, C alone can do the job in how many days?

## Ira is younger than Vivan by 7 years and their ages are in the respective ratio of 7 : 9. How old is Ira?

Ira is younger than Vivan by 7 years and their ages are in the respective ratio of 7 : 9. How old is Ira?