In the figure,two 4-digit numbers are to be formed by filling the places with digits. The number of different ways in which the places can be filled by digits so that the sum of the numbers formed is also a 4-digit number and in no place the addition is with carrying, is

There are 18 points in a plane of which 5 are collinear. How many straight lines can be formed by joining them?

"NOTRE DAME" কলেজ "BANGLADESH" এর একটি আদর্শ বিদ্যাপীঠ।

How many $3$ digit numbers can we make using the digits $4,5,7$ and $9$ and where repetition is allowed?

If $^nC_6 : ^{n - 3}C_3 = 33 : 4$, find n.