2007-06-13 13:30:21 · 5 answers · asked by nikki 1 in Science & Mathematics ➔ Mathematics
2178 * 4 = 8712
'a' must be 1 or 2 or else a 5-digit product would be formed.
but 'a' cant be 1 since d * 4 ends in 'a' and so 'a' must be even. so 'a' is 2
d must then be 3 or 8 since 4*d ends in 2. but d cant be 3 because 4*a (plus any carry) equals d so d must be at least 4. so d is 8.
at this point you can just try the other numbers for c and see what b must be. only the one combination works.
(or, if you notice that there is no carry digit with 4*b, (since 2*4=8 already) b must be 0 or 1 (2 is used already), and 0 wont work)
2007-06-13 13:42:16 · answer #1 · answered by Scott R 6 · 2⤊ 0⤋
If a, b, c and d are integers that are multiplied together, then one of them = 0.
If abcd is a four-digit number and dcba is another 4-digit number, then "a" must be either 1 or 2 (if it's anything else, you don't get a 4-digit answer)
Answer = 2178*4 = 8712
2007-06-13 13:44:53 · answer #2 · answered by Steve A 7 · 0⤊ 0⤋
If abcd are binary "digits" then if abcd = 0011, abcd x 4 = 1100 = dcba.
2007-06-13 13:42:30 · answer #3 · answered by hevans1944 5 · 0⤊ 2⤋
the answer is 2178 it took me 15 mins
2007-06-13 13:51:48 · answer #4 · answered by Da Phontom 1 · 0⤊ 3⤋
Try this site:
http://www.math.com/
2007-06-13 13:37:48 · answer #5 · answered by HappyStarz 5 · 0⤊ 3⤋