Glencoe Math: Course 1, Volume 1
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Glencoe Math: Course 1, Volume 1 View details
6. Estimate Quotients
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Exercise 3 Page 226

Use compatible numbers. Compatible numbers are numbers that are easy to divide mentally.

26

Practice makes perfect

We want to estimate a quotient using our rounding skills. Let's start by looking at the given quotient. 984.76 ÷ 38.1 Our first step is to round the divisor to the nearest whole number. We follow a couple steps to do this.

  • Look at the digit to the right of the place that is being rounded to.
    • If the digit is less than 5, then the number in the rounded place remains the same.
    • If the digit is 5 or greater, add 1 to the number in the rounded place.
  • After rounding, remove any decimal digits.In our case, the place that we are rounding to is the ones place, so we will look at the number in the tenths place. Let's round the divisor!
    We found that 38.1 rounded to the nearest whole number is 38. 38.1≈ 38 Next, we will round the dividend so that the divisor and the dividend are compatible numbers. Compatible numbers are numbers that are easy to divide mentally. The best way to know that our numbers will be compatible is to round 984.76 to a number that is a multiple of 38. Let's list some multiples of 38. Multiples of38 38, 76, ... 912, 950, 988,1026, ... The closest multiple of 38 to 984.76 is 988. Let's round 984.76 to 988 and then divide 988 by 38.

    By our estimation, 984.76 divided by 38.1 is about 26.