Two urgent Maths problem sums!?

Question

1) Joe left home for office at 8.20a.m. He drove a distance of 33km at 66km/h and took 5 minutes to walk from the car park to the office. What time did he reach the office?

2) Peter swam from one side of a river to another side at an average speed of 25m/min. As soon as he reached the other side of the river, he immediately swam back to the starting point. The whole trip took him 30 mintues. If his average speed for the whole trip was 20m/min,
a) what was the total distance he swam?
b) what was the average speed of his return trip?

P.S I don't want those like: take z as 30mins, or any other algebra methods, cos my country doesn't use these methods and my teacher doens't understand them. Thanks!

I'm from Singapore and we hardly use any algebric expressions so I cannot use the algebra methods US people use...sorry.

I'm from Singapore and we hardly use any algebric expressions so I cannot use the algebra methods US people use...sorry.

Answer 1

q1 =8.55am q2 a 600mtr b15mtr per min
i think

Answer 2

1) Joe took half an hour to drive the 33 km (33/66 = 1/2 hour) and then walked 5 minutes. So he reached his office at 8.55 a.m.

2) Peter swam the whole trip in 30 mins and the average speed was 20 m/min, so the total distance he swam is 30 multiplied by 20, 600 meters.

So, the river width is half ot it, 300 m.

Since his speed while going to the other side was 25 m/min, he took 12 mins. (300/25)

That means his return trip took him 18 mins. That gives his average speed in the return journey as 300 / 18 = 16.66 m/ min

Answer 3

1> Time in car = Distance/Speed = 33/66= 1/2 hr = 30mins
Time spent walking = 5 mins.

So he reache offce At 8.20 + .30 +.05 = 8.55am

2> Avg speed = total distance/total time

=> total distance =20 * 30 = 600m

So width of river =300m

He took 300/25 =12 mins for 1st part.

For returning, he therefore took 30-12 =18 mins

is speed was distance/time = 300/18 = 16.66 m/min


EDIT: Pretty gal, no matter how much you want to escape formulae, the fact remains that speed = distance / time, that is distance covered in unit time. So if your teacher doesn't understand that, you need to change schools.

Or switch to learning music or painting, where you don't need or could possibly have formulae. Wait. Even painting has formulae. You can get pink only if you mix red and white, and if that ain't a formula, what is? I remember my mom knitting sweaters for me, and even that required formula So the intricate design would come out perfect. Which country are you from, anyways?

Answer 4

1.) 66km/hr - 33km (to know the time he spends in driving -- 66km/hr , so in 33km he spends half an hour)

30min + 5min = 35 min.
He left home 8:20am + 35min = 8:55 am - he reached the office at 8:55am

2.) 25m/min (swam one side of a river to another side of the river) - whole trip took him 30min

a) 25m/min x 30 = 750m
b) 20m/min - average speed for the whole trip half of this is the average of his return trip = 10m/min

Answer 5

1. To find the time Joe reached the office, you need to find out the time Joe took to reach the office. You know he drove from home to the office and then walk to his office from the car park. You know he took 5 minutes to walk to his office from the car park. You would need to total up the time he took for him to drive to the office and the time he took to walk to his office from the car park. To calculate the time he took for him to drive, use this formula : Speed=Distance/Time. To get the time, bring time to left by multiplying it with speed : Speed x Ti me=Distance and send speed to th right by dividing distance with speed : Time=Distance/Speed. So,

Time= Distance/Speed
= 33/66
=0.5 hour
but since you would need to add it with the 5 minutes, change 0.5 hour into minutes. Do this by multiplying 0.5 with 60 because 1 hour=60 minutes.

0.5 x 60 minutes
=30 minutes.

Now, add the 30 minutes (home to car park) with the 5 minutes (car park to office). You'll get 35 minutes (home to car park to office).

Then add 35 minutes with 8.20 a.m. So you add 35 with 20 . You'll get 8.55 a.m. Joe reached office at 8.55 a.m.

8 . 20
35
------------
8 . 55
--------------

2.a) The average speed is 20 m/min and total time is 30 minutes. To find average speed, the formula is
Average speed=Total distance/Total time.

So, Total distance= Average speed x Total time

Total distance= Average speed x Total time
= 20 x 30
=600 m.

b) The average speed for this question is the same as the average (usual one, not the speed one-above).

Average=Total of both speeds
--------------------------
How many speeds

The total of both speeds is 25+Return trip speed and there are two speeds (first time Peter swam speed and return trip). The average speed is 20 m/min.

Average=Total of both speeds
--------------------------
Quantity of speeds

20 =25+Return trip speed
-------------------------------
2

20 x 2 = 25+Return trip speed

40=25+Return trip speed
40-25=Return trip speed
15 m/min =Return trip speed

I used the linear method, if you do not know, memorise these formulas :

Speed=Distance/Time
Distance=Speed x Time
Time=Distance/Speed
Average speed=Total distance/Total time
Total distance= Average speed x Total time
Total time=Total distance/Average speed
Average=Total of quantities/Quantities

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