From the land-sea ratio of the earth's surface of 7: 17, we can know that the proportion of global land to the global total area is 7/(7+ 17)=7/24.

The ratio of land to sea in the northern hemisphere is 7 1: 109, which means that the ratio of land in the northern hemisphere to the total area of the northern hemisphere is 71/(71+109) = 711.

Because the area of the northern hemisphere is half that of the world, the land area of the northern hemisphere accounts for 71(180 * 2) = 71/360.

therefore

The proportion of land in the global total area is 7/24-71/360 = 34/360 =17/180.

therefore

Land-sea area ratio17: (180-17) =17:16317:163?

References:

The area ratio of land and sea in the southern hemisphere is: 19: 8 1.