A number is chosen at random from all two-digit numbers. Find the probability that the number is
(a) less than 40;
(b) a multiple of 5;
(c) not a multiple of 5.

Question

A number is chosen at random from all two-digit numbers. Find the probability that the number is
(a) less than 40;
(b) a multiple of 5;
(c) not a multiple of 5.

anonymous · Answer

@ganeshie8

ganeshie8 · Answer

how many two digit numbers are there ?

ganeshie8 · Answer

and, how many two digit numbers are less than 40 ?

ganeshie8 · Answer

two digit numbers :- 10, 11, 12.... 99  
can u count them ha ? :)

anonymous · Answer

less than 40, does it means 40 also?

ganeshie8 · Answer

nope

ganeshie8 · Answer

less than or equal to 40, means 40 also

ganeshie8 · Answer

less than 40 :  10, 11, .... 38, 39

anonymous · Answer

i forgot the formula of calculating the number of terms..

ganeshie8 · Answer

there is no formula, just count them :)

anonymous · Answer

i remember it has a formula...
ok. 90 terms and 30 terms?

ganeshie8 · Answer

thats right ! for probability, take the ratio fo them

anonymous · Answer

ratio?
3:1 ?

ganeshie8 · Answer

read the question again
you are randomly pickign 2 digit numbers, and want to find the probability for it to be less than 40

anonymous · Answer

1/3

ganeshie8 · Answer

number of ways it can be less than 40 =  30
total number of ways  = 90

so probability = number of ways in favor / total number of ways
                     = 30/90
                     = 1/3

ganeshie8 · Answer

yes :) try part b

anonymous · Answer

10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95

18 terms

anonymous · Answer

18/90 = 1/5

ganeshie8 · Answer

correct !

anonymous · Answer

not a multiple of 5 = 1- 1/5 = 4/5 ?

ganeshie8 · Answer

thats right !!

anonymous · Answer

thank you so much!

ganeshie8 · Answer

np :)