I found a shorter method. Lisa has to make up 75 meters. Of her 8 mps, 5 mps maintains her distance from Sam, while the other 3 mps advances. 3 mps covers 75 m in 25 sec.
But the question wasn't "how many seconds passed from the start of the race when Lisa caught up to Sam". The question was "how many seconds have passed when Lisa caught up to Sam". As written, the answer should be 40. The 15 second head start is still time passing. That makes it an ambiguous question, and I'm surprised the test writers didn't realize that.
@@AlexxxDE That's part of the previous sentence. "Lisa runs at an average speed of 8m/s, not including the head start." Simply reaffirming that she isn't running for the first 15 seconds. There's a period in there you missed. There's no way to attach that sub-clause onto the following sentence grammatically.
That is nothing but a very simple question of relative speed . Total distance = 15x5 = 75 m and relative speed = 8 - 5 = 3 ( relative speed running in the same direction is the difference of speeds ) . The answer therefore is 75/3 = 25
Found a shorter method. A is too low and D is too high by looking at the numbers given. C looks odd because it doesn't have a 5 at the end so we strike it off and select B
I found a shorter method. Lisa has to make up 75 meters. Of her 8 mps, 5 mps maintains her distance from Sam, while the other 3 mps advances. 3 mps covers 75 m in 25 sec.
r we twins ? got the same idea, was about to say that till i saw ur comment
@anotherllllll Faster fingers won.
@@Daniel-w3h2u
XD
But the question wasn't "how many seconds passed from the start of the race when Lisa caught up to Sam". The question was "how many seconds have passed when Lisa caught up to Sam". As written, the answer should be 40. The 15 second head start is still time passing.
That makes it an ambiguous question, and I'm surprised the test writers didn't realize that.
she can’t use the exact wording cause copyright or whatever
The question reads " Not including the headstart" as a Dr. you should know to "read the question"
@@AlexxxDE That's part of the previous sentence. "Lisa runs at an average speed of 8m/s, not including the head start." Simply reaffirming that she isn't running for the first 15 seconds.
There's a period in there you missed. There's no way to attach that sub-clause onto the following sentence grammatically.
That is nothing but a very simple question of relative speed . Total distance = 15x5 = 75 m and relative speed = 8 - 5 = 3 ( relative speed running in the same direction is the difference of speeds ) . The answer therefore is 75/3 = 25
That Lisa is one fast lady as she caught her brother at the 200 metre mark within 3.7 seconds of the women's world record time.
I'd say brainstorming is also helpful it we don't have to do process and only choose from the option
(8m × ?) = (5m × ?) + 75m
Found a shorter method. A is too low and D is too high by looking at the numbers given. C looks odd because it doesn't have a 5 at the end so we strike it off and select B
‘Shorter method’ guessing
Yeah, I especially like "looks odd" as a mathematical process 😂😂
My dumb ass thinking 2😭😭😭
These questions are so easy. Probably the main reason why American students are falling behind in education.
D=5t+75
D=8t
8t=5t+75; t=25
it takes her 25 seconds to catch up. What about 15 seconds of head start? should be 40 total
8x = 5x + 75
3x = 75
x = 25 seconds
Easy problem to do in your head in even less time