To start we need to consider the possible outcomes of the second dice. It could roll a 1, 2, 3, 4, 5, or 6. There is an equal chance of each of these outcomes.
If the second dice rolls a 1, the sum of both dice is 4. Anything higher than a 1 gives us a sum higher than 4. We want sums of 4 or less. The only way to roll a 4 or lower is to roll a 1. Therefore there is 1 outcome out of the 6 possible outcomes that gives us what we want. The answer, then, is 1/6 or 0.167.
