need something explained: "Tim has a water bottle that holds 400 mill...."

[dldaily1@aol.com]

The math question reads... Tim has a water bottle that holds 400 mill. Mary has a water bottle that holds 1/5 as much. How many do they hold together? The answer is 480. But here is where I am confused(in case the numbers are more complex in the future) It reads as a division problem so to figure it out, we should multiply 400 by 5/1, which of course would be wrong. So why if it is a division problem, do we not use the reciprocal of 1/5 and multiply ?

 

[Deleted member 4993]

The math question reads... Tim has a water bottle that holds 400 mill. Mary has a water bottle that holds 1/5 as much. How many do they hold together? The answer is 480. But here is where I am confused(in case the numbers are more complex in the future) It reads as a division problem so to figure it out, we should multiply 400 by 5/1, which of course would be wrong. So why if it is a division problem, do we not use the reciprocal of 1/5 and multiply ?

Mary's bottle holds = 1/5 0F 400

= 1/5 * 400

= 80 ← OF translates to "multiplied by"

 

[Steven G]

The math question reads... Tim has a water bottle that holds 400 mill. Mary has a water bottle that holds 1/5 as much. How many do they hold together? The answer is 480. But here is where I am confused(in case the numbers are more complex in the future) It reads as a division problem so to figure it out, we should multiply 400 by 5/1, which of course would be wrong. So why if it is a division problem, do we not use the reciprocal of 1/5 and multiply ?

When you do not see why a problem is solved the way it is with 'unfriendly numbers' or you do not know how to solve the problem with 'unfriendly numbers' then replace the unfriendly numbers with friendly numbers. In your case you have only one unfriendly number--1/5. What if 1/5 was the number 2 instead, That is, Mary has a water bottle that holds 2 times as much as Tim. Would you really divide by 2 or would you multiply by 2? Just do the same with 1/5.