multiplying and summing quantity and price for 112 items

I have a dataset which includes consumption quantity and price per unit for 112 food items. Therefore, each observation has 112 variables for quantity and 112 variables for price. I want to calculate total expenditures on food by multiplying each quantity consumed with its corresponding price. I could write 112 lines of syntax, but I was wondering whether there is a faster way of doing this? I tried using the foreach command but it seems to be limited to multiplying each variable with a constant instead of each variable with a different variable. The data is structured as follows:

I want to multiply i1_1_5 (quantity) with i1_1_4 (price) for each food item, so i1_2_5 multiplied by i1_2_4 and so on for each of the 112 items.

Does anybody have any advice?

Thanks