75% of the gas pipeline has been laid, the length of which will be 102.8 km.

75% of the gas pipeline has been laid, the length of which will be 102.8 km. How many kilometers of the gas pipeline remain to be laid?

1) Let x km of the gas pipeline have already been laid. Let’s compose and solve the proportion:

102.8 km – 100%,

x km – 75%,

from here we can write that 102.8: x = 100: 75.

According to the main property of proportion, the product of its extreme members is equal to the product of the middle terms, which means:

102.8 * 75 = 100x,

7710 = 100x,

x = 7710: 100,

x = 77.1.

Consequently, 77.1 km of the gas pipeline has already been laid.

2) Let’s calculate how many kilometers of the gas pipeline remain to be laid:

102.8 – 77.1 = 25.7 km.

Answer: 25.7 km of the gas pipeline remains to be laid.