Maths problem

[West]

Need to draw model.

 

D = dry period

R = raining period

 

RRRDDDDDDDDDDDDDD Morning

DDDDDDDDDDDRRRRRR Afternoon.

 

From above, there are 8 dry days, i.e. Morning and afternoon are dry.

End to end, there are 17 days.

 

what you draw is just one possible scenario, here is some other possibilities: 

 

D = dry period

R = raining period

 

RRRDDDDDDDDDDDDDD Morning

RRRRRRDDDDDDDDDDD Afternoon.

 

RRRDDDDDDDDDDDDDD Morning

RDRRRRRDDDDDDDDDD Afternoon.

 

RRRDDDDDDDDDDDDDD Morning

RDDRRRRRDDDDDDDDD Afternoon.

 

RRRDDDDDDDDDDDDDD Morning

DRRRRRRDDDDDDDDDD Afternoon.

 

etc etc

 

Number of dry days can range from 8 to 11 days.

[Ender]

what you draw is just one possible scenario, here is some other possibilities: 

 

D = dry period

R = raining period

 

RRRDDDDDDDDDDDDDD Morning

RRRRRRDDDDDDDDDDD Afternoon.

 

RRRDDDDDDDDDDDDDD Morning

RDRRRRRDDDDDDDDDD Afternoon.

 

RRRDDDDDDDDDDDDDD Morning

RDDRRRRRDDDDDDDDD Afternoon.

 

RRRDDDDDDDDDDDDDD Morning

DRRRRRRDDDDDDDDDD Afternoon.

 

etc etc

 

Number of dry days can range from 8 to 11 days.

Read the question again please.  Rain is either morning or afternoon. There's no full day raining.

Only one answer, 8 dry days. 

Edited July 8, 2017 by Ender

[Little_prince]

My turn to ask question. Can't seem to work it out.

 

Find the missing number

 

Left              Right

8    16          12   34    

9    18            6    ?

 

Find the relationship on the left to apply to the right to get the missing number.

 

17?

[Vid]

17?

 

I never solved that so dunno the answer

 

What makes you think it's 17?

[Vid]

Time to use your brains guys.

 

Find the difference in area of A and B. Pi is 3.14

 

Pardon the erased pencil marks

Edited July 29, 2017 by Vid

[Ender]

A - B = Big quadrant - small quadrant - rectangle

 

Where

big quadrant = pi x 24 x 24 / 4

Small quadrant = pi x 12 x 12 /4

Rectangle = 24 x 12

[Lala81]

Area of A is pi x 24*24/4 minus pi*12*12/4

Area of C (the space above A) is 12*24 minus A minus pi*12*12/4

Area of B is 24*24 minus Area of C and pi*24*24/4

[Lala81]

A - B = Big quadrant - small quadrant - rectangle

 

Where

big quadrant = pi x 24 x 24 / 4

Small quadrant = pi x 12 x 12 /4

Rectangle = 24 x 12

I don't understand. B is outside the big quadrant. How can this equation work?

[Ender]

I don't understand. B is outside the big quadrant. How can this equation work?

My method is derived from visualizing an area map. I will explain later when i have access to a computer tonight. Edited July 29, 2017 by Ender

[1fast1]

Time to use your brains guys.

 

Find the difference in area of A and B. Pi is 3.14

 

IMG_4076.JPG

Pardon the erased pencil marks

 

Let x be the area of shape left by subtracting area B from the area of the rectangle (so it's the area of the figure formed by three straight edges and a curved "roof").

 

Q(n) is area of Quadrant with radius n. R is area of 24*12 rectangle.

 

Q(24) - Q(12) = A + x

R = B + x

 

Subtracting, A - B = Q(24) - Q(12) - R = 51.12 sq cm.

[Stratovarius]

A= big quad - small quad

B = rect - (big quad -A-smallquad)

 

Edit. My bad. Ender is right.

Edited July 29, 2017 by Stratovarius

[Enye]

think can change this thread title to

 

 

 

 

 

 

maths no problem

[Ender]

I don't understand. B is outside the big quadrant. How can this equation work?

This how I taught my son when I was  preparing him for PSLE two years back. Have him visualise the shape and removing them one by one. Primary level they haven't learnt complicated equation yet.

Edited July 29, 2017 by Ender

[Lala81]

This how I taught my son when I was preparing him for PSLE two years back. Have him visualise the shape and removing them one by one. Primary level they haven't learnt complicated equation yet.

Thanks. Think I got it. Though I probably will get confused again

No wonder I got B for a level maths hahaha

Let x be the area of shape left by subtracting area B from the area of the rectangle (so it's the area of the figure formed by three straight edges and a curved "roof").

 

Q(n) is area of Quadrant with radius n. R is area of 24*12 rectangle.

 

Q(24) - Q(12) = A + x

R = B + x

 

Subtracting, A - B = Q(24) - Q(12) - R = 51.12 sq cm.

This is the simultaneous equation equivalent of @ender 's solution haha

[Stratovarius]

Thanks. Think I got it. Though I probably will get confused again

A = big quad - small quad - (rect-B)

A-B = big q - small q - rect

[Vid]

This how I taught my son when I was  preparing him for PSLE two years back. Have him visualise the shape and removing them one by one. Primary level they haven't learnt complicated equation yet.

 

Good illustration Thanks!

[Lala81]

A = big quad - small quad - (rect-B)

A-B = big q - small q - rect

No I understand this time. But my mind quite one track one. Change the question a bit then I will blur liao. Hahaha thats always been my weakness.

Lol I the type need to drill until I see all variations then I can answer.

Edited July 29, 2017 by Lala81

[Stratovarius]

No I understand this time. But my mind quite one track one. Change the question a bit then I will blur liao. Hahaha thats always been my weakness.

Lol I the type need to drill until I see all variations then I can answer.

Same. Lol. My wife one look knows the ans. I need an equation for sort this out. Some ppl are more visual in this aspect.