Case 1: You start now with a yearly investment of Rs 1000 and stay invested for 40 years.
Case 2: You start after 20 years from now but invest Rs 2000 instead for 20 years.
In both the case, the amount invested is Rs 40,000. Assuming a common growth rate of 10% in both the cases, in case 1 , the accrued balance works out to Rs 442,593 . The accrued balance in case 2 is Rs 114,550.
Why don't you work it yourself and take away your learnings.