Question

first put 21 red balls 19 blue bash :
bals in the gip ( rightarrow )
21 sed bals can be praced in 1 way (auar identical)
Gaps Aeatest = Oreated = 22
( N^{prime} frac{20 j v^{2}}{r a t^{prime} cdots g}=frac{22 times 2 r^{7} times 20}{3 times 2} )
( =22 times 70 )
( =1540 )
- a antion

# 149.11 141. In how many ways 21 red balls and 19 blue balls can be arranged in a row so that no two blue balls are together? (a) 1,540 (b) 1,520 (C) 1,560 (d) None 5.19

Solution