Well we know that 2100 is divisible by 100, 21 times to be exact. Since percentage is formatted on the 100’s scale, this is optimal. What this means is that here we can say 43% of 100 is 43, then we multiply 43 by 21 since 100 fits into 2100 21 times. Doing calculations, you’ll find that 43 x 21 is 903, which happens to be our answer. This is the method I use mentally, it’s good to learn.
