2400
When you add tens to the tens digit and ones it goes ten more.
9 is in the hundreds place. The tens digit will determine whether you round this up (in which case it would become 10, which would mean zero and add 1 to the thousands digit). The tens digit is 7, so the 9 rounds up and rounded it is 5000
91
The digit of 115 in the tens place is the 1.
660
'94' rounded to the nearest tens is '90'.
135
Yes.
94
60
Look at the digit in ones place. If it is five or greater, round the digit in tens place to the next higher digit. If the digit in ones place is less than five, leave the digit in tens place as it is. 512162 rounded to the nearest tens is 512160.
89 rounds to 90
69
69 !
538 is rounded to 540 to the nearest tens digit or to 500 to the nearest hundred.
2400