what is the largest 4-digit number you can make
9876 is the largest four digit number you can make if all the digits must be different.
999next number is 1,000
For this type of "the largest number which..." questions, you need to advance from left to right, using the largest possible digit in each case. For the first two digits, that would be 9, for the third digit (the right-most digit), the largest digit which will make this possible is an 8.
348+301 can make 649