A car traveling at a certain constant speed takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 75 kilometers per hour. At what speed, in kilometers per hour, is the car traveling?
A. 71.5
B. 72
C. 72.5
D. 73
E. 73.5
Speed time distance:- Easy statement but still ????????????
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- nicktimoshenko
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75 km/h = 75*1000/3600 = 20.8 m/s
t1 = 1000/20.8 = 48s
t2 = 48+2 = 50
v2 = s/t2 = 1000/50 = 20 m/s = 72 km/h
(b)
t1 = 1000/20.8 = 48s
t2 = 48+2 = 50
v2 = s/t2 = 1000/50 = 20 m/s = 72 km/h
(b)
- indiantiger
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We know speed = distance/time
STEP 1
given to us speed = 75km/hr
distance = 1km
calculate the time = 1/75 = 1/75*3600 = 48sec
Now at the certain constant speed (x) to cover 1 km time taken is 50sec(48+2 sec)
STEP 2
distance = 1km time =50 sec
sped = d/t = 1*1000/50 = 20meters/sec
convert it to km/hr = 20/1000*3600 = 72km/hr (B)
or
AFTER STEP 1
lets try substituting the values from answer choices, we will start with B & D as values are in increasing order
For (D) 1km/73km/hr = 1*3600/73 = 49.31sec, value very close to 50 sec so in order to get the right value we need to reduce the denominator value.
Now check for (B).
1km/72km/hr = 1*3600/72 = 50 secs, thats what our value is from Step 1 hence (B)
STEP 1
given to us speed = 75km/hr
distance = 1km
calculate the time = 1/75 = 1/75*3600 = 48sec
Now at the certain constant speed (x) to cover 1 km time taken is 50sec(48+2 sec)
STEP 2
distance = 1km time =50 sec
sped = d/t = 1*1000/50 = 20meters/sec
convert it to km/hr = 20/1000*3600 = 72km/hr (B)
or
AFTER STEP 1
lets try substituting the values from answer choices, we will start with B & D as values are in increasing order
For (D) 1km/73km/hr = 1*3600/73 = 49.31sec, value very close to 50 sec so in order to get the right value we need to reduce the denominator value.
Now check for (B).
1km/72km/hr = 1*3600/72 = 50 secs, thats what our value is from Step 1 hence (B)
- harshavardhanc
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time for traveling 1 Km @ 75kmph = 60 * 60 / 75 = 48 secs.pardeep_10sharma wrote:A car traveling at a certain constant speed takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 75 kilometers per hour. At what speed, in kilometers per hour, is the car traveling?
A. 71.5
B. 72
C. 72.5
D. 73
E. 73.5
at normal speed it takes 2 secs more OR a %increase of 2/48 =1/24
which is equivalent to a 1/25th decrease in the speed or speed is 24/25 * 75 = 72 Kmph.
Regards,
Harsha
Harsha
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Thanks to all for such wonderful replies. I was making as illy mastake. Thanks to make me realize that.