Christmas MT's answer to Xanthe's Primary 5 Maths Whole Numbers question.

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Christmas MT
Christmas Mt's answer
2903 answers (A Helpful Person)
Use the formula: n/2 (a+l), where n is the number of numbers, a is the value of the first number and l is the last digit.
For eg, if the qn is 2+4+6, n will be 3, a is 2 and l is 6. So sum is 3/2 (2+6) = 12.