What I do mentally is:
If , average them and multiply by 1.4 since sqrt(2) = 1.414
If , use a * 1.2 (actual value is 1.202)
If , use , which is an upper bound
Examples
a=84, b=69. Average is 77, times 1.4 is 108, actual value is 108.7
a=48, b=18. b is maybe 35% of a, 35%^2=12, so the estimate is a * 1.06 = 51 or so. Actual value is 51.26
Not sure how they compare in accuracy but it seems like your method is simpler, at least if you remember that they cross when b is 20% of a
What I do mentally is:
If
If
If
Examples
a=84, b=69. Average is 77, times 1.4 is 108, actual value is 108.7
a=48, b=18. b is maybe 35% of a, 35%^2=12, so the estimate is a * 1.06 = 51 or so. Actual value is 51.26
Not sure how they compare in accuracy but it seems like your method is simpler, at least if you remember that they cross when b is 20% of a