Multiplication estimation example

a ticket agent sells 42 tickets to a play the tickets cost $29 each use rounding to estimate the total dollars taken in from the sale of the tickets now if we wanted the exact number we could say 42 42 times 29 and we could work out the multiplication but they essentially want us to be able to do it in our head we want to round the numbers first and then multiply so if we want to round and really we just have two places here so we're going to round anything it's going to be to the nearest 10 because that's the largest place we have so if we round 42 to the nearest 10 we've done this drill many times to in the ones place is less than 5 so we're going to round down the nearest 10 is 40 we're going to round down to 40 29 if we round to the nearest 10 9 in the ones place is greater than well greater than or equal to 5 so we round up the nearest 10 is 30 and another way to think about it just say well you know 42 that's pretty close to 40 29 is pretty close to 30 those are literally the nearest multiples of 10 that I can figure out so now I can multiply so now you can multiply and here once again we can use you could call it a trick or but hopefully you understand why it works but 30 times 40 instead you can say well this is going to be the same thing as 3 times 4 we're going to put two zeros at the end of it 30 times 40 is the same thing as 3 times 4 with two zeros so let's do that so you have 3 times 4 is 12 which we know and then we have 2 zeros we got that zero so let's take that zero there and then we get that blue zero there so let's put that over there so we're going to have they're going to have a roughly twelve hundred dollars taken in from sales of the tickets that is our estimate