Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsguru]

underthesea:

Thank you so much for answering my query. DS form teacher can't solve this problem. She said there's something wrong with the question!

Hi Underthesea,

At first, I thought the question was incomplete too (but I thought it was due to typo *no offence ya...*). Haha...like what Dharma said, the 1st scenario should have the 2 words \"each day\". And as stated in my solution, my assumption is that the no. of days is the same for both scenarios. Perhaps, that should be made clear to the students in the question. Otherwise, your DS' form teacher could be right --- the question cannot be solved. :politebleah:

Cheers,
MathsGuru

[BigDevil]

mathsguru:

My solution is the same as BigDevil. Have added explanation in my working. Hope it helps!

:oops: I knew how to work out the answer, but I couldn't quite explain myself.
If we encounter this kind of question in exams, is it sufficient to lay out the answer as I did, or must the students explain their work?

[Andaiz]

BigDevil:

mathsguru:

My solution is the same as BigDevil. Have added explanation in my working. Hope it helps!

:oops: I knew how to work out the answer, but I couldn't quite explain myself.
If we encounter this kind of question in exams, is it sufficient to lay out the answer as I did, or must the students explain their work?

BigDevil, the devil is in the details...the students are told to put down the working and/or models coz in the event that the answer is wrong (copy wrong or just plain careless), the marker can follow the logic and trend of thoughts!

[mathsguru]

BigDevil:

mathsguru:

My solution is the same as BigDevil. Have added explanation in my working. Hope it helps!

:oops: I knew how to work out the answer, but I couldn't quite explain myself.
If we encounter this kind of question in exams, is it sufficient to lay out the answer as I did, or must the students explain their work?

Hi BigDevil,

Don't worry, ur working is good enough to earn u full marks for this question. I added the explanation for Underthesea's reference.

Cheers,
MathsGuru

[quickmind]

KSP:

tamarind:

Thanks in advance. My friend sent me this question :


I am a three digit number. The digit in the tens place is 6 less than the digit in the hundreds place. The tens place is 2 more than the digit in the ones place. If the digit in the ones place is 5, then I am the number ______.

Is this a P1 question?

I think so

[BigDevil]

Andaiz:

BigDevil:

:oops: I knew how to work out the answer, but I couldn't quite explain myself.

If we encounter this kind of question in exams, is it sufficient to lay out the answer as I did, or must the students explain their work?

BigDevil, the devil is in the details...the students are told to put down the working and/or models coz in the event that the answer is wrong (copy wrong or just plain careless), the marker can follow the logic and trend of thoughts!

Thanks, Andaiz. Point noted! :salute:

[BigDevil]

mathsguru:

Don't worry, ur working is good enough to earn u full marks for this question. I added the explanation for Underthesea's reference.

That's good to hear, but glad to see your explanation. I foresee I would need to do some explaining to DD.

[mathsguru]

Hi all,


Just wanna share the solutions to some P3 questions I received from a fellow KSP member.

http://www.postimage.org/image.php?v=gxWdtoi

http://www.postimage.org/image.php?v=gxWdvTr

http://www.postimage.org/image.php?v=gxWdynA

http://www.postimage.org/image.php?v=gxWdASJ

Cheers,
MathsGuru

[Dharma]

Solutions to JA’s questions.


Q1)Find the sum of the first 100 numbers in the following number sequence.
1,2,3,4,5,6,7,8,9,1,0,1,1,1,2,1,3,1,4,1,5,…

1 to 9 = 9 numbers
1,0,1,1,12…1,7,18,1,9 = 20 numbers
2,0,2,1,2,2…2,7,2,8,2,9 = 20 numbers
3,0,3,1,3,2…3,7,3,8,3,9 = 20 numbers
4,0,4,1,4,2…4,7,4,8,4,9 = 20 numbers
Total 89 numbers

Last 11 numbers : 5,0,5,1,5,2,5,3,5,4,5

Sum of 1st 100 numbers =
1+2+3+4+5+6+7+8+9+1+0+1+1+1+2+1+3+1+4+1+5+ …+ 5+1+5+2+5+3+5+4+5

(1+2+3+…+8+9) = 45
(1+0+1+1+1+2+…+1+8+1+9) = (1x10) + 45 = 55
(2+0+2+1+2+2+…+2+8+2+9) = (2x10) + 45 = 65
(3+0+3+1+3+2+ …+3+8+3+9) =(3x10) + 45 = 75
(4+0+4+1+4+2+…+4+8+4+9) = (4x10) + 45 = 85
(5+0+5+1+5+2+5+3+5+4+5) =(5x6) + 10 = 40

Sum = 45+55+65+75+85+40 = 365

Q2)The Sentosa High School’s telephone number is an eight digit number.The sum of the two numbers formed from the first three digits and the last five digits respectively is 66558.The sum of the two numbers formed from the first five digits and the last three digits is 65577.Find the telephone number of the The Sentosa High School.

Let the telephone number be abcdefgh

defgh + abc = 66558
(10000d + 1000e + 100f + 10g +h)+(100a + 10b + c) =60000 + 6000 + 500 + 50 + 8
d = 6
1000e + 100(f+a) + 10(g+b) + (h+c) = 6000 + 500 + 50 + 8 ………………(1)

abcde + fgh = 65577
(10000a + 1000b + 100c + 10d + e)+(100f + 10g +h) = 60000 + 5000 + 500 + 70 +7
a = 6
1000b + 100(c +f) + 10(d+g) + (e +h) = 5000 + 500 + 70 + 7 ……….(2)


From (1)
1000e + 100(f+6) +10(g+b) +(h+c) = 6000 + 500 + 50 + 8 …………….(3)
f+6 = 15; f = 9
Since f = 9; e = 5

From (2)
1000b + 100(c+9) + 10(6+g) + (4+h) = 5000 + 500 + 70 + 7 ……………(4)
C + 9 = 15; c = 6
Since c = 6; b = 4

From (3)
5000 + 1500 + 10(g+4) + (h+6) = 6000 + 500 + 50 + 8
h+6 = 8
h=2
g+4 = 5
g=1

abcdefgh = 64665912

646 + 65912 = 66558… ok
64665 + 912 = 65577…ok

The telephone number is 64665912


Q3)Placed on a table is a maths problem
89+16+69+6X+Y8+88
X and Y represents a digit.
Two students A and B sit on the opposite sides of the table facing
each other.They read the problem from
their directions and both get the same answer.What is their answer?

89 + 16 + 69 + 6X + Y8 + 88 = 88 + 8Y + X9 + 69 + 91 + 68
262 + 6X + Y8 = 316 + X9 + 8Y
(6X + Y8 ) – (X9 + 8Y) = 54
X and Y can 1, 6, 8 or 9

1 and 8 looks the same when seen from both directions
6 will look like 9 to the person opposite and vice versa.

By trial and error, using X =1 & Y = 9

(61 + 98 ) – (19 + 86) = 54 —ok
89+16+69+61+98+88 = 421

[Vanilla Cake]

Hi Mathsguru,


Pls refer to http://www.orlesson.org/orp/09Ma/2009-P6-Math-SA2-PeiChun.pdf. There are no given answers for Q13 to Q18 in paper 2.
Pls kindly provide the answers for these questions. Thanks in advance.
:love: