Question

Dr. Crypto starts at 10. He skip counts by 10. What number will he reach after 8 counts?

• A. $70$
• B. $80$
• C. $90$
• D. $100$

Answer 1

The correct option is C $90$

Say: Let us skip count to find the number Dr. Crypto will reach after 8 counts starting from 10.

Steps:
$\bullet$ We know that Dr. Crypto starts counting from 10.
$\bullet$ So, the first count will be $10+10=20$ and the second will be $20+10=30$.
Similarly, the next count will be 40, then $50,60,70,80,90.$
Starting from $10$, we arrive at the number $90$ after 8 counts.
Hence, option B is the correct answer.

WB: If required, use the whiteboard to find the total number Dr. Crypto will say after 8 countings as shown.


Error Analysis Question:
Q: If Dr. Crypto starts at 10, and skip counts by 5, will he reach the number 90 after 10 counts?
A: No, if Dr. Crypto starts at 10 and skip counts by 5, the 10th number he says will be 60.