Successor and Predecessor of 99
Question
Find the successor and predecessor of 99.
Solution — Step by Step
Finding the Successor:
The successor of a number is the number that comes immediately after it. To get the successor, we simply add 1.
Successor of 99 = 99 + 1 = 100
Finding the Predecessor:
The predecessor of a number is the number that comes immediately before it. To get the predecessor, we subtract 1.
Predecessor of 99 = 99 − 1 = 98
Successor and Predecessor
Successor of n = n + 1 Predecessor of n = n − 1
Successor of 99 = 99 + 1 = 100 Predecessor of 99 = 99 − 1 = 98
Answer:
- Successor of 99 = 100
- Predecessor of 99 = 98
Why This Works
"Successor" comes from the Latin word meaning "to follow." The successor of any number is just the very next number in our counting sequence. On the number line, it is the point one step to the right.
"Predecessor" means "what came before." It is the number one step to the left on the number line.
Think of a queue outside a cinema. If you are person number 99, the person right behind you is person 100 (your successor), and the person right in front of you is person 98 (your predecessor). The queue is like a number line!
💡 Expert Tip
A good memory trick: "SUCCESSor" — the successor comes after, just like what comes after success. And the predecessor comes before — "pre" means before (like "preview" — you watch it before the main film).
Something Special About 99's Successor
The successor of 99 is 100 — a round number and a milestone in our number system. Notice that:
- 99 is a 2-digit number
- Its successor 100 is a 3-digit number
This transition from 99 to 100 is special: it is the only point where 2-digit whole numbers end and 3-digit whole numbers begin.
Similarly, the successor of 999 is 1000 (3-digit to 4-digit), and the successor of 9999 is 10000 (4-digit to 5-digit).
Common Mistake
⚠️ Common Mistake
Mistake: Confusing successor with predecessor. Some students write the successor as 98 and the predecessor as 100, which is reversed.
Remember: Successor = NEXT number (add 1). Predecessor = PREVIOUS number (subtract 1). The successor of 99 is 100 (bigger), and the predecessor of 99 is 98 (smaller).