Pri 6 maths questions

[email protected]_F3V3R SG

actually a quicker methood. ext. angle of a triangle, y = 90 + 33 <sup>o</sup>

skythewood SG

actually a quicker methood. ext. angle of a triangle, y = 90 + 33 <sup>o</sup>

yes, but i don't like to teach my student ext. angle of triangle.

if they need me to teach them, they probably is having trouble le, so i see no point teaching them this step, which is just a combination of two steps. if they can handle the other 4 types of angle relation, is enough le.

technoboy SG

Ok, last 3 questions guys before she goes for battle tomorrow!

These problems really give me an headache!

1) A cashier had 151 pieces of $50 notes and $10 notes. She took out 3/4 of the $50 notes and put in nine $10 notes. As a result, the ratio of the $50 to $10 becomes 3:8. What is the total value of the $10 notes initially?

2) The length of a bridge is 1500m. A train takes 150secs to travel on the bridge. The whole train was completely on the bridge for 100secs. Find (a) the average speed of the train and (b) the length of the train

3) P overlaps Q & R. Q is on R. Ratio of area of P, Q, R is 1:2:3. 40% of Q is shaded.Find the % of the figure unshaded.

skythewood SG

presently,

$50 ===> X X X
$10 ===> X X X X X X X X

at the beginning, before taking away 3/4 of $50

$50 ===> X X X X X X X X X X X X
$10 ===> X X X X X X X X
number of notes is 151 + 9 = 160 (include the 9 $10)

simplify diagram to

$50 ===> X X X
$10 ===> X X

one X is equal to 160/5 = 32 notes

hence, you can solve the thing

skythewood SG

a) speed = distance divide by time
= 1500 / 150
= 10m/s

b) the 100 seconds is the time between the end of the train get on the bridge, and the front of the train reach the end of the train.

distance travelled = speed x time
= 10 x 100
- 1000m

hence, the train is = 1500 - 1000
= 500m

skythewood SG

3) P overlaps Q & R. Q is on R. Ratio of area of P, Q, R is 1:2:3. 40% of Q is shaded.Find the % of the figure unshaded.

P: Q : R

1 : 2 : 3

unshaded R = 3units - 2units
= 1units

since 40% of Q is shaded, 80% of P is shaded. since ratio of P:Q is 1:2

unshaded P = 20%/100 x 1 unit
= 1/5 unit

unshaded Q = 60%/100 x 2 units
= 6/5 units

shaded Q = 40%/100 x 2 units
= 4/5 unit

total unshaded = 1 unit + 1/5 unit + 6/5 unit
= 2 and 2/5 unit

total area = 2 and 2/5 units + 4/5 units
= 3 and 1/5 units

percentage = 12/5 units divide by 16/5 units
= 75%

technoboy SG

presently,

$50 ===> X X X
$10 ===> X X X X X X X X

at the beginning, before taking away 3/4 of $50

$50 ===> X X X X X X X X X X X X
$10 ===> X X X X X X X X
number of notes is 151 + 9 = 160 (include the 9 $10)

simplify diagram to

$50 ===> X X X
$10 ===> X X

one X is equal to 160/5 = 32 notes

hence, you can solve the thing

Got this! Thanks alot!

technoboy SG

a) speed = distance divide by time
= 1500 / 150
= 10m/s

b) the 100 seconds is the time between the end of the train get on the bridge, and the front of the train reach the end of the train.

distance travelled = speed x time
= 10 x 100
- 1000m

hence, the train is = 1500 - 1000
= 500m

Hmm, this answer isn't correct leh. Answer is 12m/s for the speed of train and 300m for the length of train. Any ideas how?

technoboy SG

P: Q : R

1 : 2 : 3

unshaded R = 3units - 2units
= 1units

Can you explain this very first step? Don't quite get it. Thanks once again!

skythewood SG

Can you explain this very first step? Don't quite get it. Thanks once again!

You see Q and R in the picture?

Q is inside R. the ratio of Q:R is 2:3

the area of R that is not covered by Q is = 3units(R) - 2 unit(Q)

= 1 unit

skythewood SG

if the answer is 12m/s, than the 150 sec to travel on the bridge means the time starts when the train gets on bridge, and stops when train get off bridge.

i interpreted it as it take 150s to travel the 1500m of the bridge. sorry, my bad.

for 150 seconds, the train travel 1500m + length of train

for 100 seconds, the train travel 1500m - length of train

so in 50 seconds, the train travel twice the length of train

in 25 seconds, the train travel the length of the train.

in 125 seconds, the train travel the 1500m.

if you follow my train of thoughts, you can solve this le.

technoboy SG

Oh ok understood. Initially thought the unshaded R is inclusive of the unshaded Q area.

« Previous Page