Answer:
434
Explanation:
310 * 1.4 = 434
or if you want to break it up more:
10% of 310 = 31 (to get 10% divide by 10)
to get from 10% to 40% multiply your answer by 4
31 * 4 = 124
so 40% = 124
this means over the three months Allison's rock collection increased by 124.
to get the total amount of rocks Allison has now add the increase to the original value
310 + 124 = 434