1^st way :10 + 20 + 60 + 40 + 80 + 90

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

=30 x 10

=300

2^nd way :10 + 20 + 60 + 40 + 80 + 90

=(10 + 90) + (20 + 80)  + (60 + 40)

=100 + 100 + 100

=100 x 3

=300

We have:

x=60 : \(\dfrac{1}{3}\)=180

We have :

6.(a + 5)=90

<=>a + 5=15

=>a=10

* is 8 

=>738 :2 and 9

The circumference of circle is:

2 x 2 x 3,14`=12,56(cm)

    Answer:12,56 cm

10 + 35 + 100 : 25                                               25 + 15 + 10 + 80 : 4

=10 + 35 + 4                                                        =25 + 15 + 10 + 20

=45 + 4                                                                =40 + 30

=49                                                                      =70

The average of 5, 10, 30 is:

\(\dfrac{5+10+30}{3}\)=\(\dfrac{45}{3}\)=15

Answer:15

The average of 20, 10, 60 is:

\(\dfrac{20+10+60}{3}\)=\(\dfrac{90}{3}\)=30

Answer:30

The average of 23, 67, 108 is:

\(\dfrac{23+67+108}{3}\)=\(\dfrac{198}{3}\)=66

Answer:66

\(\sqrt{3375}\)=\(15\sqrt{15}\)

x - \(\dfrac{7}{5}\)=\(\dfrac{3}{7}\)

x=\(\dfrac{3}{7}\) + \(\dfrac{7}{5}\)

x=\(\dfrac{64}{35}\)

1st way :10+ 20 + 30 + 40 + 50 + 60 + 70 + 80

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

=36 . 10

=360

2ndway:10 + 20 + 30 + 40 + 50 + 60 + 70 + 80

=(20 + 80) + (30 + 70) + (40 + 60) + (10 + 50)

=100 + 100 + 100 + 50

=300 + 60

=360

1^st way :10+ 20 + 30 + 40 + 50 + 60 + 70 + 80

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

=36 . 10

=360

2^ndway:10 + 20 + 30 + 40 + 50 + 60 + 70 + 80

=(20 + 80) + (30 + 70) + (40 + 60) + (10 + 50)

=100 + 100 + 100 + 50

=300 + 50

=350

100 + 200 + 300 +  500 + 700 + 800 + 900                     200 + 300 + 400 + 100 + 700 + 600 + 900

=(100 + 900) + (200 + 800) + (300 + 700) + 500      =(300 + 700) + (400 + 600) + (100 + 900) + 200

=1000 + 1000 + 1000 + 500                                      =1000 + 1000 + 1000 + 200

=3000 + 500                                                              =3000 + 200

=3500                                                                        =3200

10 + 20 + 30 + 40 + 50 + 60 + 70 + 80 + 90 + 100

=(10 + 90) + (20 + 80) + (30 + 70) + (40 + 60) + (50 + 100)

=100 + 100 + 100 + 100 + 150

=100 . 4 + 150

=400 + 150

=550

Their total ages in three years time is: 31 + (3 . 3)=40(years)

Answer:40  years

1000+2500+2000+8000+7500+9000                             105+120+480+395

=(1000+9000)+(2500+7500)+(2000+8000)                   =(105+395)+(120+480)

=10000+10000+10000                                                   =500+600

=30000                                                                            =1100

The volume of the figure is:

[(8 . 4) : 2] . 10=160 (cm³⁾

Answer:160 cm³

M=\(\dfrac{5}{7}\) . \(\dfrac{5}{11}\) + \(\dfrac{5}{7}\) . \(\dfrac{2}{11}\) - \(\dfrac{5}{7}\) . \(\dfrac{14}{11}\)

   =\(\dfrac{5}{7}\) . (\(\dfrac{5}{11}\) + \(\dfrac{2}{11}\) - \(\dfrac{14}{11}\))

  =\(\dfrac{5}{7}\) . \(\dfrac{-7}{11}\)

  =\(\dfrac{-5}{11}\)

A=\(\dfrac{1.1.2.2.3.3.4.4}{1.2.2.3.3.4.4.5}\)=\(\dfrac{1}{5}\)

=>A=\(\dfrac{1}{5}\)