Quantitative Aptitude - Arithmetic Ability Questions

We know that zero can't be in hundreds place. But let's assume that our number could start with zero.

The formula to find sum of all numbers in a permutation is

111 x no of ways numbers can be formed for a number at given position x sum of all given digits

No of 1 s depends on number of digits

So,the answer us

111 x 20 x (0+1+2+3+4+5) = 33300

We got 20 as follows. If we have 0 in units place we can form a number in 4*5 ways. This is for all numbers. So we have substituted 20 in formula.

Now, this is not the final answer because we have included 0 in hundreds place. so we have to remove the sum of all numbers that starts with 0.

This is nothing but the sum of all 2 digits numbers formed by 1 2 3 4 5. Because 0 at first place makes it a 2 digit number.

So the sum for this is 11 x 4 x (1+2+3+4+5).
=660

Hope u understood why we use 4. Each number can be formed in 4x1 ways

So, the final answer is 33300-660 = 32640

Let the marked price of the router be Rs. P

From the given data,

$$\begin{gathered} P x 85100 - P x 80100 = 51 \\ P x 5100 = 51 \\ ⇒ P = 51005 = 1020 \end{gathered}$$

Hence, the original marked price of the router is Rs. 1020.

From the given data,

when my age is 24, my mothers age is double of my age 

=> 48 yrs is my mothers age

=> Difference is 48 - 24 = 24 years.

When my age is 44

=> My mother is 44 + 24 = 68 years aged.