Hello,
Answer of challenge question 5
3 ab * 61=19947
First of all, see the digit in the units place of the answer.It is 7.
Applying “Last by Last”sutra,we get b=7.
Now,
3 a*7* 61=19947
21a*61= 19947
Applying digit sums,
digit sum of 19947=3(casting out 9’s)
Numbers Digit sums
21a 3+a
61 * 7 *
——– ———
19947 3
In the digit sums column,
(3+a) * 7 = 3
21 * 7a =3
again, applying digit sums,
3 * 7a=3
for this to be true, 7a=9,implies a=2
so the smudged digits are b=7 and a=2
327 * 61=19947
Thanks
