If the weight of 90 books is 50kg, what is the weight of 180 such books. In both proportion and unitary method.

See explanation

Step-by-step explanation:

From the question, we are informed that the weight of 90 books is 50kg. We need to get the weight of a book first and this will be:

= 50/90

= 5/9

Therefore, the weight of 180 such books will be 5/9 multiplied by 180. This will be:

= 5/9 × 180

= 100kg

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so: