Dao Trong luan was wrong

20 + 30 + 40 + 50 + 60 + 70

=(30 + 70) + (40 + 60) + (20 + 50)

=100 + 100 + 70

=270

Cho mình nói tiếng việt nha:

Thì ra Dao Trong Luan là người chuyên tự đánh dấu

We have: 234567² - 234557 . 234577

= 234567² - (234567 - 10) . (234567 + 10)

=234567² - (234567² - 10²)

=10² =100

The answer is: (7 - 3) x 50 = 200

\(\dfrac{1}{2}\) + \(\dfrac{1}{6}\) + ... + \(\dfrac{1}{30}\) + \(\dfrac{1}{42}\)

=\(\dfrac{1}{1.2}\) + \(\dfrac{1}{2.3}\) + ... + \(\dfrac{1}{5.6}\) + \(\dfrac{1}{6.7}\)

=\(\dfrac{1}{1}\) - \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) - \(\dfrac{1}{3}\) + ... + \(\dfrac{1}{5}\) - \(\dfrac{1}{6}\) + \(\dfrac{1}{6}\) - \(\dfrac{1}{7}\)

=\(\dfrac{1}{1}\) - \(\dfrac{1}{7}\)

=\(\dfrac{6}{7}\)

450 + 20 + 50 + 80 + 100

=(450 + 50) + (20 + 80) + 100

=500 + 100 + 100

=700

The number of seconds does Candace run ahead Vicky is:

29 minutes 46 seconds - 28 minutes 47 seconds = 59 seconds

                Answer: 59 seconds

The sum of the degree measures of the interior angles of a regular octagon is:

                 180^o(8 - 2) = 1080^o

                                    Answer: 1080^o

3x + 160

=3x +155 + 5

=272 + 5

=277

a : 4=> a : ?

We have: 4=2 x 2        4=1 x 4

=>a : 1, 2, -1, -2 

10 + 20 + 30 + 40 + 50 + 60 + 70 +80 + 90  

=(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9) x 10

=45 x 10

=450

10 + 20 + 30 + 40 + 50 + 60

=(1 + 2 + 3 + 4 + 5 + 6) x 10

=21 x 10

=210

The average of 10 + 10 + 10 is:

\(\dfrac{10+10+10}{3}\) = \(\dfrac{30}{3}\) = 10

  Answer: 10

The rectangle perimeter is :

(12 + 8) x 2=40 (cm)

    Answer: 40 cm

The average of 6, 8, 16 is:

\(\dfrac{6+8+16}{3}\) = \(\dfrac{30}{3}\) = 10

Answer: 10

100 : 5 + 50 : 5

=20 + 10

=30

That 's right

You should not do that

100: 5 + 50: 5

= (100 + 50) : 5

=150 : 5

=30

There are members in the family kangaroo is:

2 + 3 + 2=7(nembers)

Answer: 7 members

The calculate average of 4, 15, 35 is:

\(\dfrac{4+15+35}{3}\) = \(\dfrac{54}{3}\) = 18