Quote:
Originally Posted by skawal
S=1-(1/2)+(1/3)-(1/4)+(1/5)-(1/6)+(1/7)-(1/8)+(1/9)-(1/10)
S=(1/2)+(1/3)-(1/4)+(1/5)-(1/6)+(1/7)-(1/8)+(1/9)-(1/10)
S= (1/2)[1+1/2 +1/3 +1/4 +1/5] +1/3 +1/5 +1/7+1/9
keep special eye to the bold terms.from the term you can see that this term [1+1/2 +1/3 +1/4 +1/5] is greater than 1 and 1/2 of these is greater than 1/2.if we add this number(greater than 1/2) with the another term [1/3 +1/5 +1/7+1/9] then we get a number that is also greater than 1/2.
so the ans is A.
for the first problem
1+2+3+4+5..........+47+48 separate it with the sum of the even integers and the odd integers.then we get
2+4+............+48 and 1+3+................47
no.of terms is = (24-1)+1=24 for both the cases.
sum of the even integers= [2*2 +(24-1)2]*24/2=300=V
sum of the even integers= [2*1 +(24-1)2]*24/2=288=D
so we can see that D+23 is greater than V.
For the last problem
72.42=k(24+ n/100) from the problem if k and n are positive integers and n is less than 100 you can easily make an assumption that k must me a number which is 3 to make balance of the equation that means 3*24 is equal to 72 and 3*(n/100) will give you .42
3*(n/100)=.42
so,n=14
so,k+n=14+3=17. 
give me response whether im correct or not. |
Actually, I read a better way to answer this kind of a question elsewhere. Notice, that every time a greater term is getting added than the term that is being subtracted. And, we see that the first 2 terms are 1-1/2= 12/. From, after that we have 1/2 + ( 1/2-1/4+1/5..) ie. 1/2 + ( bigger term - smaller term ). Therefore, S is greater than 1/2