Question 611614
I would write the numbers in a form that is easier to visualize: plain numbers with commas separating the thousands.
Those planets are all only a few thousands of kilometers wide, so the numbers do not get too long. It's also good to put them in order, smallest to largest.
 
Mars: {{{6.88*10^3}}} = 6,880
Venus: {{{1.21*10^4}}} = 12,100
Neptune: {{{4.95*10^4}}} = 48,500
Saturn: {{{1.21*10^5}}} = 121,000

Mars is the smallest of the planets listed. The next smallest one is Venus.
Neptune is larger, and Saturn is the largest one. Having them in order, each planet will be closer in size to the ones listed next to it than to the other planets. 
 
The difference between the diameters of Mars and Venus is
12,100 Km - 6,880 Km = 5,220 Km,
and Venus is not quite twice as wide as Mars,
so the absolute difference and the relative difference are rather small.
For any other pair of planets, those differences are larger.
 
The difference between Venus and Neptune is
49,500 Km - 12,100 Km = 37,400 Km,
and Neptune is more than four times as wide as Venus.
 
The difference between Neptune and Saturn is
121,000 Km - 49,500 Km = 71,500 Km,
and Saturn is more than twice as wide as Neptune.