I really need help

[BikBoi]

So I have a maths assignment that requires me to use matrices on excel, however when I am multiplying them using the mmult formula it only fills out 1 single rectangle and not a whole new matrix, I have to do it manually for each row as it won't let me do the whole thing at once, I have to do a Leslie matrix of over 150 years and it will take too long. 

[#2]

@BikBoi 

Select a range of the appropriate size (same number of rows as the first matrix, same number of columns as the second matrix).

Enter the MMULT formula and confirm it with Ctrl+Shift+Enter to turn it into an array formula.

If you just press Enter or Tab, you'll just enter the formula in the active cell, and it won't be an array formula.