Sol. Ans.(c). Digits used in the first row are 2, 3, 7 and 9. Possible numbers 237, 239, 273, 279, 293, 297, 327, 329, 372 … and so on 24 numbers are possible. But you see, answer of thrice the number greater 329 would be in four digits (372×3 = 1116), that is not our case. So, we have possible numbers for the first row are 237, 239, 273, 279, 293, 297, 327, 329.
Repetition of digits is not allowed. So, if we will take 237, 476 (two times).. 7 is repeated, failed. 239 – two time is 478 and three time is 717, repetition error. 273 – two time = 546, three time = 819, no digit is repeated, so 273 is a valid number. 279 – two times = 558, repetition error. 293 – two times = 586, three times 879, repetition error. 297 – two times = 594, repetition error. 327 – two times 654 and three times = 981 is a valid number. 329 – two times = 658, but three times = 851, will have repeated digit.
So, only two such cases are possible
Case I - First row – 273; Second row – 546 and Third row - 819
Case II – First row – 327; Second row – 654 and Third row – 981.