A series is given with one term missimg. -40, -81, -164, -329, -660, -1321, ?

Solution

Series:
-40, -81, -164, -329, -660, -1321, ?

Check the pattern carefully:

• $-40 \times 2 -1 = -81$
• $-81 \times 2 -2 = -164$
• $-164 \times 2 -1 = -329$
• $-329 \times 2 -2 = -660$
• $-660 \times 2 -1 = -1321$

Pattern: multiply by 2 and subtract alternately:

$-1,,-2,,-1,,-2,\dots$

Now find the next term:

$-1321 \times 2 -2$

= -2642 -2

= -2644

✅ Missing term = -2644