FINDING AN AVERAGE 173 Four girls of the fourth grade are weighed by the school nurse. Mary weighs 65 lb., Jane weighs 61 lb., Elizabeth weighs 64 lb., and Kathleen weighs 62 lb. How much do the four girls weigh together? If you divide the total weight of the girls by the number of girls whose weights were added, your answer should be their average weight. Miss Smith, the nurse, says it is 63 lb., and very good. Do you get the same average weight for the girls that Miss Smith got? 1. John lives 4 blocks from school; Eric lives 5 blocks from school; Tony lives 6 blocks from school. Miss Jones, the principal, wants to know the average distance the boys live from school. What answer would you give? 2. Ethel kept a record of the number of examples that she worked correctly in 3 tests. In the first one she got 9, in the second 12, and in the third 12. What was the average number that she worked correctly? 3. Can you make a rule for finding an average? 4. Mr. Wilson says his team of horses will average 1,400 lb. apiece. What does he mean by that? May one horse weigh more than 1,400 lb. and the other one less? Explain. 5. Another school wants to play your baseball team, if it doesn't average more than 67 lb. a boy. If each boy in the class will find out his own weight to the nearest pound, you should be able to find the average weight of 9 boys to make a baseball team. Can you do that? 6. A baseball pitcher pitches 7 times to the first man, 2 times to the second man, 6 times to the third man, once to the fourth man, and 9 times to the fifth man. What is the average number of times that he pitches to a man? Check your answers to all of the other examples above to see if the following rule is always true: To check subtraction, add the difference to the subtrahend. The sum should be the same as the minuend. day cake. Her grandmother blew out 27 of them at one time. How many candles were left lighted? 176 THE TWO-FIGURE MULTIPLIER Multiply 37 by 45 37 45 185 product of 5X37 1480 product of 40×37 1665 product of 45X37 In practice always use the form below: 37 45 185 148 1665 product Multiply: 5 times 7 ones are 35 ones, or 3 tens and 5 ones. Write the 5 under the ones and remember the 3 tens. 5 times 3 tens are 15 tens. Adding the 3 tens we have 18 tens, or 1 hundred and 8 tens. Write 8 tens under the tens, and the 1 hundred under hundreds. 40 times 7 ones are 280, or 2 hundreds, 8 tens, 0 ones. Write 8 under the tens and remember the 2 hundreds. 40 times 3 tens are 120 tens or 12 hundreds. 12 hundreds plus 2 hundreds are 14 hundreds. Write the 4 under hundreds, the 1 under thousands. Adding we have 16 hundreds, 6 tens, and 5 ones, or 1665. |