Q. If 4 whole number are taken at random and multiplied together , what is the probability that the last digit in the product is 1,2,7 or 9?

Option
a)15/653
b)12/542
c)16/625
d)17/625
please explain the numerical
answer is (c)

• consider 4 numbers as ABCD for any multiplication of numbers we will get last digit only in between 0,1,2,3,4,5,6,7,8,9.but we want the last digit 1,2,7 or 9.here the probability is 4/10.
  1)fix BCD values and vary A value we get prob 4/10.
  2)fix ACD and vary B value prob is 4/10.
  3)fix ABD and vary C value prob is 4/10.
  4)fix ABC and vary D value prob is 4/10.
  product of prob=4/10*4/10*4/10*4/10==256/10000=16/625.
• 11 years agoHelpfull: Yes(4) No(0)