Ah - the words of digiyoof...
PPRune Pop, remember the old '60 mph is 88 ft/sec' thing from prep school?
Call 3 mph 1/20th of 60 mph, then that's 4.4 ft/sec
25 yds is 75 ft.
Time is dist/speed, thus time is 750/44 sec.
Which is 1/4 of 750/11
Say after me, "Eleven into 75 is 6, carry 8. 11 into 90 is 8, carry 2, eleven into 20 is - call it 2.
So that's 68.2 divided by 4
Which is a tadge over 17 sec.
Or at 4 mph, 3/4 of that - so that's seven threes are 21 plus 30 equals 51 divided by 4. Twelve fours are 48, so that's 12 3/4 sec.
For digiyoof, make that 12.78409090909090 sec.....
Calculators - Bah, humbug!
And, another useful prep school piece of knowledge, a yard was actually the distance between Henry VIIIth's extended forefinger with his arm outstretched to his side parallel to the ground and the tip of his nose. Ask PPRuNe Pop - he was probably there at the time!