Use rounding to estimate the answer to the subtraction
problem.

47 - 12	??? 40 30 10 70 20 60
89 - 47	??? 40 30 10 70 20 60
77 - 38	??? 40 30 10 70 20 60
97 - 41	??? 40 30 10 70 20 60
51 - 32	??? 40 30 10 70 20 60
81 - 57	??? 40 30 10 70 20 60
38 - 11	??? 40 30 10 70 20 60
92 - 78	??? 40 30 10 70 20 60
87 - 79	??? 40 30 10 70 20 60
87 - 17	??? 40 30 10 70 20 60