19,20,21
40 * * * * * The correct answer is 6400.
The sum of the first 20 even numbers... is 110
2+4+6+8+10........+40=420
You can use the formula for the sum of an arithmetic series to calculate that quickly. (Of course, you can also type the numbers into Excel, and get the sum - but that doesn't scale well - e.g., it won't work well if you are then asked, for instance, to get the sum of the first million even numbers.)
The sum of the first 40 odd numbers is 1,600.
The sum of the first 40 even numbers is 1,640.
19,20,21
40 * * * * * The correct answer is 6400.
The sum of the first 20 even numbers... is 110
1 ,3, 5, 7 ,9......, 77, 79. Sum of first 40 odd numbers is 1600. This is the answer
The sum of the numbers 1 to 39 = 39 x 40 ÷ 2 = 780 The sum of the numbers 1 to 60 = 60 x 61 ÷ 2 = 1830 Therefore the sum of the numbers 40 to 60 = 1830 - 780 = 1050
2+4+6+8+10........+40=420
Sum of numbers = 40 Count of numbers = 4 Average = Sum/Count = 40/4 = 10
The sum of the first 50 whole numbers is 1,225.
The sum of the first 1,000 whole numbers is 499,500.
The average of five numbers whose sum is 200 will always be 40, no matter which numbers you choose. When finding an average, you add up the numbers (find the sum of the set), then divide by the number of terms. In this case, the sum will always be 200, and there will always be five terms. This will always result in an average of 40. Ex/ 1 + 2 + 3 + 4 + 190 = 200 200 / 5 = 40 40 + 40 + 80 + 24 + 16 = 200 200 / 5 = 40