If two similar springs each of spring constant K 1 are joined in series, the new spring constant and time period would be changed by a factor:

Step-by-step solution

1 k e q = 1 k 1 + 1 k 2 1 k e q = 1 k + 1 k ⇒ k e q = k 2 k ' = k 2 T = 2 π M k T ' = 2 π M k ' ⇒ T ' = 2 π M k × 2 T ' = 2 T