In few questions we need to compute the answer in modulo 10^9+7 . How to do that? Do we just need to find modulo of ans with 10^9+7 i.e. ans%1000000007 ?

you are correct that we have to find ans% (10^9 +7), but in such questions the val of ans becomes so large(it won't fit in long long) that if you just calculate the actual ans and then modulo it in the final step you will get a wrong result. Hence, in such questions you have to apply modular properties.

Some of the properties which are generally used are :

1. (a + b) % c = ((a % c) + (b % c)) % c
2. (a * b) % c = ((a % c) * (b % c)) % c
3. (a - b) % c = ((a % c) - (b % c) + c) % c

preda2or00:57, Oct 12Shubham Kumar Guptayou are correct that we have to find ans% (10^9 +7), but in such questions the val of ans becomes so large(it won't fit in long long) that if you just calculate the actual ans and then modulo it in the final step you will get a wrong result. Hence, in such questions you have to apply modular properties.

Some of the properties which are generally used are :

1. (a + b) % c = ((a % c) + (b % c)) % c

2. (a * b) % c = ((a % c) * (b % c)) % c

3. (a - b) % c = ((a % c) - (b % c) + c) % c

Follow this link for more details : modulo 10^9 + 7

Please make sure the answer is not too short