Some of the examples seem pretty easy, ex. 15 tennis balls weigh 60 ounces, how many ounces do 5 tennis balls weigh? It seems he gave up and guessed at the answer on that one.
This is a perfect example of a case when plugging in easy numbers would illuminate what needs to be done. The first thing your child needs to see is that we need to know how much one tennis ball weighs (well, okay, you could do it another way, but for sake of simplicity). He probably sees this, or my DD would have). But how do we get that number? It's interesting that you say he has good number sense because to me, a child with great number sense would know (mine might not have). Regardless, you could approach this problem by saying okay, let's try it like this--2 tennis balls weigh 10 ounces. Oh, your brain says intuitively, so obviously one tennis ball weighs 5 ounces. Wait, but how did I actually get that number? Looks like I divided the second number by the first. So I will need to divide 60 by 15 to know how much each tennis ball weighs, and then I can proceed to find out how much 4 weigh.
