1+2+3+4+5+6+…… +How much is 78 + 79 + 80? There must be a calculation process

1+2+3+4+5+6+…… +How much is 78 + 79 + 80? There must be a calculation process

1+2+3+4+5+6+…… +78+79+80
=(1+80)x80÷2
=81x40
=3240

Can 8.79-6.78-0.99 be easily calculated?

8.79-6.78-0.99 = 2.01-(1-0.01)=2.01-1+0.01=1.02

New concept 2 lesson 79 lesson 80

79: over off in up after off down in 80: on duty on second thoughts on purpose on foot on the whole on any account on the average

1 + 2 + 3 + 4 +. + 78 + 79 + 80 + 79 + 78. + 4 + 3 + 2 + 1 = {} the simple formula is: {}

1+2+3+4+.+78+79+80+79+78.+4+3+2+1
=1+79+2+78+3+77+.+79+1+80
=80+80+.+80
=80*80
=6400

What is the result of dividing 4 by 5 and multiplying 10 by 9?

4 * 5 / 4 = 5 5 * 9 / 10 = 4.5 (or 4 and 1 / 2)

(1) What is the difference between the sum of 1.8 and 17 out of 10 (2) what is the product of the quotient of 5 out of 9 multiplied by the reciprocal of 11 out of 9

1、（1.8+17/10）-（1.8-17/10）
=（1.8+1.7）-（1.8-1.7）
=3.5-0.1
=3.4
2. (5 / 9) × 9 / 11 (calculated by dividing 5 by 5 / 9)
=5×9/5×9/11
=81/11
2. (5 / 9 △ 5) × 9 / 11 (calculated by dividing 5 / 9 by 5)
=5 / 9 × 1 / 5 × 9 / 11 (approximately)
=1/11

What's the quotient of the product of one-half times the sum of two fifths and four fifths minus nine fifths?

Use 2 / 1 * (5 / 2 + 5 / 4) = 10 / 6
10 / 6 △ 20 / 9 = 10 / 6 * 9 / 20 = 3 / 4 = 1 and 3 / 1

1.2 divide the quotient of 4.23 and add the product of 5.8 and 6.3. What is the sum?

4.23 △ 1.2 + 5.8 × 6.3 = 3.525 + 36.54 = 40.065 answer: sum is 40.065

What is the sum of 6 divided by 1.5 quotient plus 2.5 times 1 / 4

6÷1.5＋2.5×1/4
=4+0.625
=4.625

What's the difference between the product of 12 and 3 minus the quotient of 75 and 25!

12×3-75÷25
=36-3
=33