The American Optometric Association suggests that children should have their first regular eye exam at six months of age. Another vision exam should take place when a child is around two or three years of age when their vision undergoes its most rapid development and vision correction is most effective.
The ISNUMBER function is a quick, easy way to check if a cell contains a number. Our example used the IF function to illustrate how ISNUMBER can be used. If you haven't used IF in a formula before, you can read our lesson on the IF function here.
Each cell has a numbered address and can store a single number. The computer can be instructed to put the number 123 into the cell numbered 1357 or to add the number that is in cell 1357 to the number that is in cell 2468 and put the answer into cell 1595..