a wall has to be painted with 7 stripes.the painter has 3 colors (red,blue,yellow)but each only enough for 4 stripes.in how many ways can he paint the wall using only two colors?

• answer is 210
  we can select 2 colors from 3 in 3C2 ways
  now from 7 positions first of all select (7C4)for one color which will color 4 strips then the other one has option of only (3C3) so (7C4*3C3)
  now we can arrange those colors in 2!ways since the 4 strips which are colored with one color may be colored with another so
  2!(7C4*3C3)=70 and since color can be chosen in 3 ways so
  3*70=210 is the answer.
• 11 years agoHelpfull: Yes(48) No(1)
• no of ways of choosing 2 color is 3c2=3;
  now we have to choose from thes two color which will be used for 4 strip i.e 2c1=2;
  now 7!/(4!*3!)=35;
  total=35*3*2=210;
• 9 years agoHelpfull: Yes(1) No(0)
• like first we can select 2 colors out of three in 3 ways now we need to find the combinations so that is 7!/4!*3!
  so 3*7!/4!*3!=105
• 11 years agoHelpfull: Yes(0) No(24)