How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

John was a very careless driver, so his owner Jacob gave him an offer that he will get an incentive of Rs.30 for every bottle box he delivered without breaking it and he will be charged Rs.90 for every bottle box he broke. Jacob gave John 100 bottles-box to deliver. After delivery, Jacob paid John Rs.2400. How many bottles-box did John break?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

Which three-digit number, made of consecutive digits, like 567, is 2 less than a cube and 2 more than a square?

Can you find out which number multiplied by itself will give the output as 12345678987654321?

Place a mathematical symbol between the numerals 5 and 9 in such a way that the resulting number is greater than 5 but smaller than 9.

We know that the number 7 is the prime followed by a cube. Which next number is also a prime followed by a cube?

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.