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[kancheongmum]

hi all need help in this speed question

last monday morning, edward walked from home to school. for the first 2 mins, he was walking at an average speed of 40 m/min. when he realized that he was going to be late by 3 mins, he quickly increased his speed by 10m/min. as a result, he was early by 1 min. find the distance between his home to school. (ans 880 m)
thanks

[maths6a]

starlight1968sg:

Hi folks,

I need some help here:

Mary has a total of 156 red and blue pens in the ratio 7:6. After giving away an equal number of each type of pen, the number of red and blue pens left was in the ratio 7:3. How many pens did she did away altogether?

Many thanks.

Since equal number of pens were given away, the DIFFERENCE between each type of pen will STAY the SAME.
7-6 = 1 unit (difference at first)
7 + 3 = 13 (total number of units at first)
156/13 =12 (1 unit at first)
7-3 = 4 (difference after)
12/4 = 3 (1 unit after)
7+3 = 10 (total number of units after)
10 x 3 = 30 were left
156 - 30 = 126 were given away in all

[blessedami]

kancheongmum:

hi all need help in this speed question

last monday morning, edward walked from home to school. for the first 2 mins, he was walking at an average speed of 40 m/min. when he realized that he was going to be late by 3 mins, he quickly increased his speed by 10m/min. as a result, he was early by 1 min. find the distance between his home to school. (ans 880 m)
thanks

Hi kancheongmum,
My DS got the answer like this:
He used algebra:

Let the time from which he left home to the expected time at school be x

Let Distance between school and home be y

Since he will reach 3 mins late if he travels the whole distance at 40m/min

(x+3)min x 40m/min= y m
(40x+120) = y m ( Equation 1 )

If he travels the first 2 mins at 40m/min and then travels the rest at
50m/min and be 1 min early,

2min x 40m/min + (x-2-1) min x 50m/min= y m
80m + ( x- 3 ) min x 50 m/min = y m
80m + ( 50x – 150 ) m = y m ( Equation 2 )

Comparing Equations 1 and 2

(40x+120) = y m ( Equation 1 )

80m + ( 50x – 150 ) = y m ( Equation 2 )

(40x+120) = 80 m + (50x- 150 )
= (50x+70)
10x = 120+70=190
x= 190÷10= 19 min
y= 80 m + ( 50 m/ min x 19 min- 150 m)
= 80 m + ( 950m- 150 m)
= 80 m + 800m
= 880 m

[maths6a]

kancheongmum:

hi all need help in this speed question

last monday morning, edward walked from home to school. for the first 2 mins, he was walking at an average speed of 40 m/min. when he realized that he was going to be late by 3 mins, he quickly increased his speed by 10m/min. as a result, he was early by 1 min. find the distance between his home to school. (ans 880 m)
thanks

2 min x 40m/min = 80 m already walked

Let the remaining time he has to reach his destination be x min.
Walking at 40 m/min, he will need (x + 3) min so idstance travelled will be
40(x + 3) = 40 x + 120 (D1)

but when he walked at 50 m/min
he will take (x - 1)min
so distance travelled will be
50(x - 1) = 50 x - 50 (D2)

since D1 = D2
40x + 120 = 50x - 50
10 x = 170
x = 17 min
total distance = 17 x 40 + 120 + 80 already travelled
= 880 m

[Dharma]

kancheongmum:

hi all need help in this speed question

last monday morning, edward walked from home to school. for the first 2 mins, he was walking at an average speed of 40 m/min. when he realized that he was going to be late by 3 mins, he quickly increased his speed by 10m/min. as a result, he was early by 1 min. find the distance between his home to school. (ans 880 m)
thanks

Hi kancheongmum,

Distance travelled by Edward in 2 mins = 40m/min x 2 min = 80m

After 2 mins; his distance to school is the same regardless of whether he increases his speed or not.

Speed ratio => 4 : 5
Time ratio => 5 : 4
5u - 4u = 1u = 4min
5u = 20 min
Distance = 40km/h x 20 min = 80

Distance from home to school = 80m + 800m = 880m

[Dharma]

starlight1968sg:

Hi folks,

I need some help here:

Mary has a total of 156 red and blue pens in the ratio 7:6. After giving away an equal number of each type of pen, the number of red and blue pens left was in the ratio 7:3. How many pens did she did away altogether?

Many thanks.

Red : 84 - 1u = 7p
Blue : 72 - 1u = 3p

84 - 7p = 72 - 3p
4p = 12
1p = 3

No. pens given away = 2 ( 72 - 9) = 2 x 63 = 126

[maths6a]

Hi some of us cannot seem to agree with the answer to this question so pls help:-

John was in the middle of a flight of stairs. He went up 3 steps, came down 5 and then up 8 and he was at the top. How many steps were there on the flight of stairs.

Many thanks

Oh and can some one tell me how I can make attachments when I have diagrams to questions? Thanks

[starlight1968sg]

Thanks so much to those who have spent their time to share their solutions.

[Dharma]

maths6a:

Hi some of us cannot seem to agree with the answer to this question so pls help:-

John was in the middle of a flight of stairs. He went up 3 steps, came down 5 and then up 8 and he was at the top. How many steps were there on the flight of stairs.

Many thanks

Oh and can some one tell me how I can make attachments when I have diagrams to questions? Thanks

You are in the middle position

Next determine your position when you move up or down withbrespect to the middle position.

Move up 3 stairs =>Middle position + 3 stairs
Move down 5 stairs => Middle position - 2 stairs ( 2 stairs below the middle position) . Move down 3 stairs to reach middle position and move down another 2 stairs
Move up 8 stairs => Middle position + 6 (move up 2 stairs to reach middle position, then move another 6 stairs to reach the top)

Total number of stairs = ( 6 x 2 ) + 1 = 13

[Dharma]

maths6a:

Oh and can some one tell me how I can make attachments when I have diagrams to questions? Thanks

Hi maths6a,

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