We know that the required number divides 372 (378 − 6) and 504 (510 − 6).
∴ Required number = HCF (372, 504)
On applying Euclid's algorithm, we get:
372) 504 (1
− 372
132) 372 (2
− 264
108) 132 (1
− 108
24) 108 (4
− 96
12) 24 (2
− 24
0
Therefore, the HCF of 372 and 504 is 12.
Hence, the required largest number is 12.