The guess-and-test strategy may be made easier by using the choices. A. 38 sixth graders ----> 57 - 38 = 19 . There are 19 seventh graders. This option already satisfy the condition that the number of sixth graders should be twice that of the seventh graders. There is no need to test for the remaining choices. The answer is letter A.
it can't be any negatives because the questions asking how many ladder rungs he climed not how far he went down. It can't be the first one cause Yan did not climb 16 rungs.
