Answer:
1) 199
2) 899
Step-by-step explanation:
1)
The 2-digit number is the number formed from unit-digit and ten-digit
∵ The greatest digit is 9
→ To form the greatest 2-digit number use 9 as ten-digit and unit-digit
∴ The greatest 2-digit number is 99
The 3-digit number is the number formed from unit-digit, ten-digit, and hundred-digit
∵ The smallest digit is 0
→ To form the smallest 3-digit number use 0 as ten-digit and unit-digit,
we can not use 0 for the hundred-digit so use 1 as hundred-digit
∴ The smallest 3-digit number is 100
∵ The sum of them = 99 + 100
∴ Their sum is 199
2)
→ To form the greatest 3-digit number use 9 as hundred-digit, ten-digit,
and unit-digit
∴ The greatest 3-digit number is 999
∵ The smallest 3-digit number is 100
∵ The difference between them = 999 - 100
∴ The difference between them = 899
