Directions: Solve the series to answer the following question. Series I: 60,…
2023
Directions: Solve the series to answer the following question. Series I: 60, 120, 24, 48, 9.6, 19.2 | Series II: 100, W, X, Y, Z, 32 (both series follow the same pattern). If a new series starts with the value of (W - X) following the same logic as above, then what is the 3rd term of the newly formed series?
- A.
120
- B.
121
- C.
144
- D.
64
- E.
25
Attempted by 1 students.
Show answer & explanation
Correct answer: D
Concept
In an alternating-operation number series, two operations are applied turn by turn in a fixed repeating cycle. Identify the repeating cycle of operations from the known terms, then apply that exact same cycle to any new starting value.
Application
Work the series step by step:
Find the rule of Series I: 60 to 120 = multiply by 2; 120 to 24 = divide by 5; 24 to 48 = multiply by 2; 48 to 9.6 = divide by 5; 9.6 to 19.2 = multiply by 2. So the repeating cycle is: multiply by 2, then divide by 5.
Apply the same cycle to Series II from 100: W = 100 x 2 = 200; X = 200 / 5 = 40; Y = 40 x 2 = 80; Z = 80 / 5 = 16; next = 16 x 2 = 32, which matches the given last term and confirms the rule.
Compute the new starting value: (W - X) = 200 - 40 = 160.
Build the new series from 160 using the same cycle (multiply by 2, then divide by 5): 1st term = 160; 2nd term = 160 x 2 = 320; 3rd term = 320 / 5 = 64.
Cross-check
The cycle (multiply by 2, then divide by 5) is preserved at every step, and the verified last term of Series II (32) confirms the rule. Hence the 3rd term of the new series is 64.