00:01
Hi there, so for this problem, we are told that a contractor requires a cement mist that is 70 % sun and 30 % cement.
00:09
He has 1 ,400 kilograms of a cement that is 80 % sand and 20 % cement.
00:21
So we have 80 % sun and 20 % so this is sand and 20%.
00:31
This is cement.
00:35
So the question is how much cement should he add to this 1 ,400 kilogram cement, so that he gets the required mix.
00:46
And we are given some options for the solution of this.
00:51
Now, we know that initially the mass of sun is going to be 0 .8 times the value given of 1 ,400 kilograms.
01:04
So from this product we obtain a mass of, so the mass that we obtain from this is equal to 1 ,120 kilograms.
01:18
And then if the 1 ,120 kilograms of sand represents the total sand in the 8 to mistur, we have to create the equation of the 7 -3 mixture as follows.
01:33
So the sound amount continues the same, but the total amount of the mixture and the salmon will change.
01:42
So we will have the following.
01:46
We will have that this is 0 .7 times the mixture mast, and this plus 0 .3 times the misture mast, and then this should be equal to just simply the mass of the mixture.
02:14
Now, by replacing in here the values, so we will have, for the first in here, we know that this remains the same, 1 ,120 kilograms.
02:30
Now in here, we'll have 0 .3, so that will be the 1 ,400 kilograms times the added mass of cement, so let's call this mc...