A concrete mixture is to be made which contains 34% sand by weight, and 627 kg of mixture containing 27% sand is already on hand. How many kilograms of sand must be added to this mixture to arrive at the required 34%?

Treat the percents given in this exercise as exact numbers, and work to three significant digits.

2

Answers

  • Brainly User
2016-03-11T05:55:49+05:30
Solutions 

A concrete mixture needs 34% of sand and there is already 27% added. To find the answer you have to subtract the percents to find how much more you need. Since we can not subtract percents the way they are we have to make them into decimals. 

Calculations 

To make a percent into decimal you have to divide by 100. Percent = out of 100. 

34% 
34 ÷ 100 = 0.34 

27%
27 ÷ 100 = 0.27 

The decimals are 
34% = 0.34 
27% = 0.27  

To find the answer we have to subtract the decimals now. 
0.34 - 0.27 = 0.07 

Now we make 0.07 to a percent. To make a decimal to percent you multiply by 100. 

0.07 x 100 = 7 

0.07 = 7%

You need to add 7% of sand more to the mixture. 




0
the answer should in kg,and if by 7% you mean 43.9 kg,its wrong
Oh sorry about that. Let me give you answer in kg.
2016-03-11T09:07:22+05:30
Since total mixture=627
in which sand is 27%
so,sand=627/100×27
=169.29kg
since 27%=169.29kg
so,1%=169.29/27=6.27kg
now,6.27×7=43.89kg
0
your answer has 4 significant figures,and if u mean 43.9,its wrong