Bob the builder is making 4890kg of concrete mix. concrete is made by mixing cement, sand and gravel in the ratio 1 : 3 : 4 how much sand does he need?

To answer this item, we are first to determine the common factor between the amounts of the cement, sand, and gravel.

If we let x be this factor, the amount of the cement would be x. Similarly, the amount of sand is 3x, and lastly the amount of gravel is 4x. Then, we establish the equation that would let us relate the amounts.

      x + 3x + 4x = 480

Simplifying,

    8x = 480

     x = 60

Hence, the amount of cement is 60 kg, that of sand is 180 kg. Lastly, the amount of gravel is 240 kg. 

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Step-by-step explanation:

let soccer = x and golf = y

part a

1st equation: x + y = 125

2nd equation: x = y +45

part b

replace x in the 1st equation with the 2nd one:

y + 45 + y = 125

simplify:

2y + 45 = 125

subtract 45 from each side:

2y = 80

divide both sides by 2:

y = 80/2

y = 40

she plays golf for 40 minutes.

part c

no because she plays soccer for 45 minutes longer than golf 40 +45 =   85 minutes, not 80 minutes.

answer: y = -12x + 108

step-by-step explanation: do (y = m x+b) formula.