To estimate 1/8 + 1/4, let's think about a whole pie. 1/8 of the pie is a pretty small slice, and 1/4 is twice that amount! Notice that this is very close to 1/2, so I would say 1/2. To estimate 4/5 - 1/2, we will use what the example says. 1/2 is closer to 4/5 than 0, so it is approximately 0.
For number 4, 1 3/8 is approximately 1, and 2 3/5 is approximately 2, so the estimate is 2-1 or 1.
To estimate 1/5 + 3/7, let's round both. 1/5 is pretty much 0, so we will let that be 0. 3/7 is very close to 1/2, so we will round that to 1/2. 1/2-0 is now easy, it is just 1/2.
For 2/5 + 2/3, do the same thing. 2/5 is near 1/2, and 2/3 is closer to 1/2 than 1, so that is also 1/2. Now, we add these up to get 1.
For 2 2/3 + 3/4, we will have 2 1/2 and [either 1/2 or 1]. When we round, if we have something that is halfway, we round it up, so we have 2 1/2 + 1 or 3 1/2.
For 1 7/8 - 1 1/2, we have that 1 7/8 is almost 2, and 1 1/2 is just 1 1/2, so we have 2 - 1 1/2 or 1/2.
Finally, 4 1/8 is around 4, and 3/4 is almost 1, so it is 4 - 1 = 3.
