Question

What percentage of a mixture of sand, gravel and cement containing
cement should be replaced by pure
cement in order to produce a mixture that is 40% cement? Show solution pls​

Answer 1

Answer: 14.29

Step-by-step explanation:

0.7x=0.6

x=0.8571 x 100 = 85.71%

100% (pure cement) - 85.71% = 14.29

Answer 2

Given,

The mixture contains 30 percent cement.  

(This information is missing in the question. Please note)

To find,

The percentage of a mixture of sand, gravel, and cement containing  30 percent cement that should be replaced by pure  cement to produce a mixture that is 40 percent cement.

Solution,

The percentage of a mixture of sand, gravel, and cement containing  30 percent cement that should be replaced by pure  cement to produce a mixture that is 40 percent cement will be 14.29 percent.

We can simply solve the question by the following method.

We know,

The mixture contains 30 percent cement.

Percentage of other materials except for cement = 70 percent

We have to produce a mixture with 40 percent cement and 60 percent other materials.

Let us assume x to be the percentage of mixture which is to be added.

Thus,

⇒ 70 x =  60

⇒ x = $\frac{6}{7}*100$

      = 85.71 percent

Now,

The percentage of a mixture of sand, gravel, and cement containing  30 percent cement that should be replaced by pure  cement to produce a mixture that is 40 percent cement will be ( 100 - 85.71 ) percent.

This will be 14.29 percent.