Model Method - Questions and Answers

Question posted by Manojkumar from Singapore:

Grade/Level: Unknown

Question solved by Model Method: the sum of 4 numbers is 121. the first number is 9 more than the second number. the third number is 5 less than the second number. the forth number is 3 times that of the first number. what is the first number?


Answer:


Step 1: Draw a box to represent the second number. Draw another box which is "9" longer to represent the first number.

model-method-questions-and-answers-291


Step 2: Draw a third box which is "5" shorter than the second number to represent the third number.

model-method-questions-and-answers-292


Step 3: Draw the set of 3 boxes representing the first number 3 times to represent the fourth number which is 3 times greater than the first number.

model-method-questions-and-answers-293


Step 4: Draw a bracket to the extreme right to represent the total of the 4 numbers which is 121.

model-method-questions-and-answers-294


From the model, subtract all the known parts from the total of 121 to get the total of all the 6 unknown parts.

121 - (5 X 5) - (4 X 9) = 121 - 25 - 36 = 60

6 units ----------> 60

1 unit ----------> 60 / 6 = 10

10 + 5 + 9 = 24

Therefore, the first number is 24.






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