Grade 5 Math Problem Calculate 1 2 3 4 5 6 99 ?

By: Love in o love you |Level 4 | 2011-6-6 23:38（1+99）x99÷2

100x99÷250x99

Reason: You look at the beginning and the end, 1+99=100, 2+98=100, 3+97=100......So they can be seen as a whole (1+99) so there are 99 2 groups, why, because there are 99 numbers here, and every 2 numbers can form a group, so there are 99 2 groups.

or = (number of first digits + number of last digits) x number of terms 2 = (1 + 99) * 99 2 = 4950

It can be 1+2+3+4+5....99=

Adding up and down is summing in reverse order.

And finally 99 out of 100 and divide by 2

The front one plus the one at the back.

100+……100 + 50 (49 100 plus one 50).

The formula for summing the difference series is n*(n+1) 2=99*(99+1) 2=99*50=4950

Add the beginning and the end by dividing the number by 2

This is the sum of the sequence:

Formula: SUM = (first term + last term) Number of items 2

Original: 1+2+3+4+5+6.....99

1 1099) 10 (2 1098) ....Ten (49 dec. 51) ten 50100 49 dec. 50

100x49 ten 50

4900 out of 10

Please refer to it!

1 1099) 10 (2 1098) ....Ten (49 dec. 51) ten 50100 49 dec. 50

100x49 ten 50

4900 out of 10

Solution: Law 1 99...2+98……48+52..49 + 51 are equal to 100, that is, 99 numbers, one 50, one number, more than 98 2 (1 9) 49 100

1＋99）x49＋50

You can put 1+2+3+....+99 is seen as 50 100s, and 1+2+3+....There is only one 50 in +99, so the final result is to subtract 50, so we get:

Original 5ox99 4950

1+2+3 +98+99 is the difference series. The sum of its first n terms is the product of the middle value (50) and the total number of terms (99).

The sum of the first and last is 100, and there are 99 2 such numbers. So 100 99 2 = 4950.

1 1099) 10 (2 1098) ....Ten (49 dec. 51) ten 50100 49 dec. 50

100x49 ten 50

4900 out of 10

Or use n(n+1)2

Get 99(99+1) 2=4950

Let's take the equation 1+2+3+4+5+6 ......... first99 is written as (1+99)+(2+98)+(3+97)+(4+96)+(5+95)+(6+94)....+50

Then the equation = 100 49 + 50

The final equation = 4900 + 50 = 4950

This is the sum of the series of equal differences.

First + Last) Number of Terms: 2

Add one head and one tail in turn, a single 50, as follows:

The answer is to add the first and last digits multiplied by 49 plus 50, and generally half of the numbers are multiplied by the sum of the first and last digits plus the middle number.

1+2+3+4+5+·· 50 Simple calculations can be performed by following these steps:

Find the sum of the roll:

First + Last) Number of Terms: 2

First term (first number) = 1

Last letter file item (last digit big open finger) = 100

Number of items (how many numbers) = 100

So (1+100)*100 2=5050

Analysis: 1 to 100 a total of 100 numbers, the beginning and end of each add, such as 1 + 100, 2 + 99, all the way to 50 + 51, divided into 50 items, the value of each Fan Dan is 101, then 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + ...100=101*50=5050。

1+100）dao+（2+99）+（3+98）+.50+51) Extended Data: A Simple Calculation Method:

1. "Rounding up and ingenious calculation" - the commutative law of addition and the combination law of state disturbance.

Make the calculations. 2. Use the commutative law and associative law of multiplication to perform simple calculations.

3. Use the properties of subtraction macro or for simple calculation, and pay attention to the reverse progress.

4. Use the nature of division to make a simple calculation (divide by a number, first multiply the reciprocal of a number, and then distribute).

5. Use the multiplicative distributive law.

Make a simple calculation. 6. Mixed operation (according to the law of mixed operation).

There is no one rule for your equation, how can you determine the next one?

If you keep subtracting after that, it will end up being a negative number.

1+2-3+4+5-6-……Pai Xinliang -99 = 1-1 + 9 - (6 + 7 + 8 + 9 + ......99)=9-105×94÷2=9-105×47=9-4935=-4926。You refer to the slow answer of the dust kuan!

If it's topical.

Add directly, the result = (1 + 99) + (2 + 8) + (3 + 7) + (4 + 6) + 5 = 100 + 10 + 10 + 5

If it is the following formula for summing the difference series.

The first term plus the last term is multiplied by the number of terms divided by two.

Analysis: 1 to 100 a total of 100 numbers, add each of the beginning and end, such as 1 + 100, 2 + 99, until 50 + 51, divided into 50 items, the value of each item is 101, then 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + ...100=101*50=5050。

1+2+3+4+5+6+7+8+9+10+…+100=（1+100）dao+（2+99）+（3+98）+.50+51）

This kind of calculation problem is called "equal difference series", which can be calculated by quick calculation, and the calculation method is:

Add the sum of the head number and the mantissa first, the head number 1 + the mantissa 50 = and 51.

The mantissa is folded in half, that is, divided by 2, 50 2 = 25 (that is, the sum of the equal difference series is the sum of 25 heads and tails) The comprehensive calculation formula of quick calculation: (1 + 50) * (50 2) = 51 * 25 = the sum of quick calculations 1275