The divisibility rule for 7 dictates that a number is divisible by 7 if subtracting 2 times the digit in the one's column from the rest of the number, now excluding the one's column digit, yields a number that is divisible by 7 or 0. Divisibility rules are simple rules that can be used to quickly determine if a number is divisible by a smaller number without a calculator.
Know MoreTo determine if the number 672 is divisible by 7, start by multiplying the last digit by 2, which in this case results in 4. Subtracting this from the rest of the number, 67 minus 4, yields 63. Since 63 can be divided by 7 evenly to result in 9, it is simple to conclude that 672 is divisible by 7.
Learn more about ArithmeticRound a number to the place value of an underlined digit by leaving the underlined digit unchanged or increasing it by one and then changing all the digits to the right of it into zeros. Determine if the underlined digit should be increased or left alone by focusing on the digit directly to its right.
Full Answer >There are 720 different combinations for a seven-digit number. This answer can be found using the (n[n-1][[n-2] ... to k factors)/k!, where n is the possible number of digits and k is the number of digits in the number. For a seven-digit number, the formula is 10!/7!.
Full Answer >Some simple rules for subtracting integers have to do with the negative sign. When two negative integers are subtracted, the result could be either a positive or a negative integer.
Full Answer >Vedic mathematics is the name given to an ancient system of Indian mathematics that's based on simple rules and principles. Its premise is that any mathematical problem, such as arithmetic, algebra, geometry or trigonometry, can be solved orally by using 16 Vedic sutras. These sutras are short, poetic phrases describing one-line formulas that allow for natural ways of solving mathematical problems.
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