Look at this series: 80, 10, 70, 15, 60, ... What number should come next?

Given data

• Sequence: 80, 10, 70, 15, 60, ...

Concept/Approach
Two interleaved patterns: first, numbers decreasing by 10; second, numbers increasing by 5.

Step-by-step calculation
First subsequence (positions 1,3,5,...): 80 → 70 → 60 → (next 50)Second subsequence (positions 2,4,6,...): 10 → 15 → (next 20)Next overall term corresponds to the second subsequence: 20

Verification/Alternative
Listing pairs: (80,10), (70,15), (60,20), ... confirms the pattern.

Common pitfalls

• Continuing with 50 immediately; that would be the term after next.

Final Answer
20