Read the row of digits below from left to right.
0 3 6 6 5 1 7 6 3 9 2 6 1 3 5 6 9 0 0 3 6 6 2 7 6 3 4
How many 6s in this row have a prime digit (2, 3, 5 or 7) directly before them and an odd digit directly after them?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 4
Check every 6 in the row: the digit before it must be 2, 3, 5 or 7, and the digit after it must be odd.
Place 3: 3 6 6 — does not count (followed by 6, an even digit)
Place 4: 6 6 5 — does not count (preceded by 6, which is not prime)
Place 8: 7 6 3 — counts
Place 12: 2 6 1 — counts
Place 16: 5 6 9 — counts
Place 21: 3 6 6 — does not count (followed by 6, an even digit)
Place 22: 6 6 2 — does not count (preceded by 6, which is not prime)
Place 25: 7 6 3 — counts
So the answer is 4.