Percents and increasing Speed

[rbansal]

I am stuck on how to solve this problem mathematically. I solved it using logic because I guessed the answer had to be slightly over 35%. However I could not do the calculations can someone show me the step by step calculations.


Q: If a bicyclist in motion increases his speed by 20% and then increases his speed by another 15% what percent of the original speed is the total increase in speed?

A) 20%
B) 35%
C) 38%
D) 65%
E) 135%


Thank you in Advance

RB

[HSPA]

let the orignal speed = 100 units
20% increase = 120 units
+15% more increase = 138

How much % is 38 in 100.. is 38%

[manpsingh87]

I am stuck on how to solve this problem mathematically. I solved it using logic because I guessed the answer had to be slightly over 35%. However I could not do the calculations can someone show me the step by step calculations.


Q: If a bicyclist in motion increases his speed by 20% and then increases his speed by another 15% what percent of the original speed is the total increase in speed?

A) 20%
B) 35%
C) 38%
D) 65%
E) 135%


Thank you in Advance

RB

its a question of series percentage increase..!!!

direct formula that we can employ to evaluate the overall percentage increase= x+y+xy/100

here x represents first percentage increase=20%, y represents second percentage increase=15;

therefore overall percentage increase= 20+15+20*15/100=38

[nkaur]

Hi i ve got another question: Do you learn the most common fractions converted into decimals by heart? Like for example 6/8? Or how do you manage ?

[Stuart@KaplanGMAT]

Hi i ve got another question: Do you learn the most common fractions converted into decimals by heart? Like for example 6/8? Or how do you manage ?

Hi,

it's very useful to know the basic fraction-decimal-percent conversions by heart, namely:

1/2 = .5 = 50%
1/3 = .333 = 33.3%
1/4 = .25 = 25%
1/5 = .2 = 20%
1/6 = .1667 = 16.67%
1/8 = .125 = 12.5%
1/9 = .111 = 11.1%
1/10 = .1 = 10%
1/20 = .05 = 5%

(1/7 = approx .14 = approx 14%)

If you know the "one overs", you can quickly figure out the other ones as required. For example, if you know that 1/8 = .125 and you need to find 5/8, you can just multiply .125 by 5 to get .625.

Also, for the ones with bigger denominators, you can often relate them to simpler fractions. For example, 1/8 is half of 1/4; 250/2 = 125, so 1/8 must be .125. Similarly, 1/9 is a third of 1/3; 333/3 = 111, so 1/9 must be .111.

If for some reason you need to convert a weird fraction, you can use good ol' long division. Remember, 5/11 is simply 5 divided by 11!