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**1. Homework Statement**

A particles position is given by r=42t^2i + 41t^3j + 6k. Calculate the magnitude of its acceleration at time t = 15 seconds

**2. Homework Equations**

**3. The Attempt at a Solution**

to find the acceleration i found the second derivative which i had as 246t + 84. Then i put 15 in as t and got 3774, but according to the answers i should get 3691. What did i do wrong