(a) The LCM of 6, 7, 8 , 9 and 10 = 2520 The greatest number of 6 digits = 999999 Dividing 999999 by 2520, we get 2079 as remainder. Hence, the 6-digit number divisible by 2520, is (999999 – 2079), or 997920. Since 6 – 4 = 2, 7 – 5 = 2, 8 – 6 = 2, 9– 7 = 2, 10– 8 = 2, the remainder in each case is less than the divisor by 2. ∴the required number = 997920 – 2 = 997918