1) √40*√490 2) √10*√640 3)√2.5*√40 4)√6.4*√90 5)√18*√32 6)√8*√800 7)√4.9*√0.9 8)√12.1*√0.4

1) √40*√490
=√4*10*49*10=2*10*7=140

2) √10*√640
=√10*64*10=10*8=80

3)√2.5*√40
=√25*4=5*2=10

4)√6.4*√90
=√64*9=8*3=24

5)√18*√32
=√9*2*2*16=3*2*4=24

6)√8*√800
=√8*8*100= 8*10=80

7)√4.9*√0.9
=√49*0.1*9*0.1=7*0.1*3=2.1

8)√12.1*√0.4 =√121*0.1*4*0.1=11*0.1*2=2.2