Select the number from among the given options that can replace the question mark (?) in the following series. 30, 20, ?, 60, 140
30
Let's solve the given number series: 30, 20, ?, 60, 140, and determine which number should replace the question mark (?) in the series.
We need to identify the pattern in the series to find the correct missing number.
- From 30 to 20: The difference is 30 - 20 = 10, which indicates a decrease.
- Now we have the unknown number which we'll denote as x. The sequence moves from x to 60.
- To deduce the pattern, let's identify the difference from 60 to 140. 140 - 60 = 80. This shows an increase in the series.
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Observing the shift from each pair of numbers, the indication is that the series alternates between decreasing and increasing.
Thus, the plausible pattern seems to be a decrease by 10, and then an increase (20 to ?) should be based on maintaining a systematic sequence with the next part being 60.
Hence, from 20, decreasing by 10 follows naturally, so x = 30.
So, the series completes as 30, 20, 30, 60, 140. Each step from one term to the next maintains either a decrease or increase by a specific rule. Hence, the answer is:
Correct Answer: 30
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