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## Topic : Types of Numbers and Number Sense

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**Topic: Types of Numbers and Number Sense**Purpose: (a) To understand the many different types of numbers. (b) To develop your “number sense” so you can understand and communicate better. Question: (a) What is your “strategy” for communicating clearly with numbers?**Rational Numbers**Natural: 1,2,3,4,5…. Whole: 0 + Natural 0,1,2,3,4,5…. Integers: Negative and Positive Whole Numbers …-4,-3,-2,-1,0,1,2,3,4… Rational: Natural, Whole, Integers Fractions and Decimals**Irrational Numbers**Irrational: (a) It is a “never ending” decimal EX/ 2.3936773519097432….on and on Can not be written as a “fraction” EX/ = 1.414213….never ending this can not be put into a fraction**What are all numbers called???*****including ALL rational and irrational numbers*** Real Numbers!….Real Numbers!!…Real Numbers!!!…Real Numbers!!!!**So what is the difference between the following?**½ 2) 0.5 3) 50% 4) 2:4 5) 50/100 ratio b) rate c) percentage d) fraction e) proportion The answer is : They are all the _________________!!! Or wait….maybe there is a difference? Don’t forget the Question we are responsible to know by the end of our lesson?!? Question: (a) What is your “strategy” for communicating clearly with numbers?**Significant Figures**Coming from the left, the firstnon-zero digit is the first significant figure and then count all the numbers going towards the right as significant figures as well Ex. 310.45 start counting from 3 until the 5 5 significant figures 0.003250 start counting from 3 until the 0 4 significant figures 1.324028 start counting from 1 until the 8 7 significant figures**Significant Figures: How to read a decimal!!!**To read and write decimals, use the following steps:Step #1: First, read the digits to the left of the decimal point as a whole number.Step #2: Say and for the decimal point.Step #3: Read the digits to the right of the decimal point as a whole numberStep #4: Say the place name of the last digit.Examples:25.578 is read twenty five andfive hundred seventy eight thousandths7000.14 is read seven thousand andfourteenhundredths0.002 is read twothousandthsNotice that there is no need to say zero and two thousandths. 250.00035 is read two hundred fifty andthirty five hundred-thousandths**1: Take a three digit numbers. (eg: 123) 2: Now reverse the**digits. (reverse of 123 is 321) 3: Now, subtract smaller number from bigger number. (in our case 321-123=198) 4. Now reverse the digits in step 3. (ie 198 becomes 891) 5. Now, add 891 and 198. 6. The answer is _______________**Age Calculation Tricks:Step1: Multiply the first number of**the age by 5. (If <10, ex 5, consider it as 05. If it is >100, ex: 102, then take 10 as the first digit, 2 as the second one.)Step2: Add 3 to the result.Step3: Double the answer.Step4: Add the second digit of the number with the result.Step5: Subtract 6 from it.**Trick 1: 2's trickStep1: Think of a number .Step2: Multiply**it by 3.Step3: Add 6 with the getting result.Step4: divide it by 3.Step5: Subtract it from the first number used.