correct
approach?
@saurabhlumarrai said:Find the sum of 7+77+777+...777...(99 times)?a)(7/9)[10(10^99-1)-891]b)(7/81)[100(100^99-99)-891]c)(7/81)[10(10^99-1)-891]d)(7/81)[100(10^99-1)-2673]e)(7/81)[10(100^99-1)-2673]
a simpler approach is consider n=99 n x=7
now if i put n=1 the sum should be 7
consider option a) (7/9)[10(10^1-1)-9(i.e 891=99*9 in our case it becomes 1*9)] = 63
b)(7/81)[100(100^1-1)-9]= ruled out as this is not equal to 7
c)(7/81)[10(10^1-1)-9] = 7 (keep it for the moment)
d)(7/81)[100(10^1-1)-27(guess why this 27 came?)] = ruled out as this is not equal to 7
e)(7/81)[10(100^1-1)-27] = ruled out as this is also not equal to 7.
hence option C has to be the right answer
now if i put n=1 the sum should be 7
consider option a) (7/9)[10(10^1-1)-9(i.e 891=99*9 in our case it becomes 1*9)] = 63
b)(7/81)[100(100^1-1)-9]= ruled out as this is not equal to 7
c)(7/81)[10(10^1-1)-9] = 7 (keep it for the moment)
d)(7/81)[100(10^1-1)-27(guess why this 27 came?)] = ruled out as this is not equal to 7
e)(7/81)[10(100^1-1)-27] = ruled out as this is also not equal to 7.
hence option C has to be the right answer
@Todd said:Approach (striking off the options)lets consider for 7 + 77 + 777 + .... 77(9 times)7(1+ 11+ 111 + .... 1111 (9 times))7( 123456789)Now if you add one more number that is (7777 (10 times)) The sum will become7(1234567890)For entire series then the sum will be like 7(1234567890.... (10 times))Multiply and divide 9 to the above number7/9 * (11111111010 (10 times)Again multiply and divide 9 then,7/81 * (99999999090 (10 times))Looking at the option I choose C as the close to answer don't know weather it's right or wrong.Let me know if you have a better approach. I am also looking into a better and faster approach.
check this out-
7 + 77 + 777 + .... 77(99 times)
=7(1 + 11 + 111 + .... 11(9 times))
=7/9(9 + 99 + 999 + .... 9999(9 times))
=7/9[(10-1)+(100-1)+(1000-1)+......]
=7/9[(10+100+1000+....)-(1+1+1+...)]
=7/9[10(10^99-1)/(10-1) - 99]
=7/9[10(10^99-1)/9-99]
=7/81[10(10^99-1)-99*9]
=7/81[10(10^99-1)-891]
7 + 77 + 777 + .... 77(99 times)
=7(1 + 11 + 111 + .... 11(9 times))
=7/9(9 + 99 + 999 + .... 9999(9 times))
=7/9[(10-1)+(100-1)+(1000-1)+......]
=7/9[(10+100+1000+....)-(1+1+1+...)]
=7/9[10(10^99-1)/(10-1) - 99]
=7/9[10(10^99-1)/9-99]
=7/81[10(10^99-1)-99*9]
=7/81[10(10^99-1)-891]
In the famous Harrods museum, the value of each of a set of gold coins varies as the square of its diameter, if its thickness remains constant and it varies as the thickness if the diameter is const. if the diameter of the two coins are in ratio 4:3. what should be the ratio of their thickness be if the value of the first is 4 times that of the second?
@IIM-A2013 said:@iLoveTorrescorrectapproach?
relative speed of the two trains = speed(fast train) - speed(slow train) = 40kmph
Now given that the slower train is twice as long as the faster train so the length of slower train=2x and faster train=x
Given the faster train over takes the slower train in 54 sec so from the relative speed calculate the distance traveled in 54sec it comes out to be 600m. so this is eqal to 3x. Therefore x=200(length of faster train)
now the length of the bridge is 400+length of train is 200=600m
hence from the speed of faster train(i.e 80kmph) find the time taken
Now given that the slower train is twice as long as the faster train so the length of slower train=2x and faster train=x
Given the faster train over takes the slower train in 54 sec so from the relative speed calculate the distance traveled in 54sec it comes out to be 600m. so this is eqal to 3x. Therefore x=200(length of faster train)
now the length of the bridge is 400+length of train is 200=600m
hence from the speed of faster train(i.e 80kmph) find the time taken
@IIM-A2013 said:An express train travelling at 80kmph overtakes a goods traain,twice as long and going at 40kmph on a parallel track,in 54 sec.How long will the express train take to cross a station 400m long?a)36sec b) 45s c)27s d)none
Option C
@IIM-A2013 said:In the famous Harrods museum, the value of each of a set of gold coins varies as the square of its diameter, if its thickness remains constant and it varies as the thickness if the diameter is const. if the diameter of the two coins are in ratio 4:3. what should be the ratio of their thickness be if the value of the first is 4 times that of the second?
whats the OA for this question?
@IIM-A2013 said:In the famous Harrods museum, the value of each of a set of gold coins varies as the square of its diameter, if its thickness remains constant and it varies as the thickness if the diameter is const. if the diameter of the two coins are in ratio 4:3. what should be the ratio of their thickness be if the value of the first is 4 times that of the second?
9/4 is the ratio?
kailash gives 1/3 of his money to keshav. keshav gave 3/4 of his money to sanket.if sanket got 900 less den kailash had, how much keshav get from kailash
600
300
400
none
@Cat.Aspirant123 said:kailash gives 1/3 of his money to keshav. keshav gave 3/4 of his money to sanket.if sanket got 900 less den kailash had, how much keshav get from kailash600300400none
@Cat.Aspirant123 said:steps
let amount with kailash be 1200x so he gave 400x to keshav and keshav gave 300x to sanket now difference between kailash and sanket is 900 u can find x'
@Cat.Aspirant123 said:kailash gives 1/3 of hismoneyto keshav. keshav gave 3/4 of his money to sanket.if sanket got 900 less den kailash had, how much keshav get from kailash600300400none
ans 400? it should be 1200. so 1/3 of it is 400. am i right?
@vbhvgupta said:For a candidate to be selected at a junior management position in a company, he must be a Mechanical Engineer or have a diloma from ITI with at least 60% marks.have secured at least 60% marks in the selection test.have scored at least 50% marks in the interview.be not less than 23 years of age and not more than 30 years of age on 1.10.2012.have completed course on CFM.If the candidate satisfies all conditions expect C, but has cleared the course of NCFM, his/her case should be referred to the HR head.If the candidate satisfies all conditions expect D, but has two years of work experience in the mechanical industry, his/her case should be referred to the General Manager.Based on the above information, decide the course of action.Mark option:(1) If the candidate is to be selected(2) If the candidate is to be rejected(3) If the case to be referred to the General Manager.(4) If the case to be referred to the HR headAkshay got 62% marks in the selection test and scored 51% in the interview. He has an ITI diploma with 65% marks. His date of birth is 23rd September 1982. He has completed his course on CFM and has 3.5 years of work experience in company XYZ, which is one of the biggest mechanical companies of the country. He has also cleared the course of NCFM.1) 1 2) 2 3) 3 4) 4
2 hai kya answer?
