Dharma:

maths6a:

Hi Can anyone help with this question?

How many 3-digit number combinations are there on a 3-digit number lock if all the 3-digits used are different and the numbers are greater than 800?

Thanks.

Digit in hundreds place => 8 or 9
Digit in tens place => 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9
Digit in ones place => 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9

Since the 3 digits used are different, you have 2 choices for hundreds place, 9 choices for tens place(1 choice already selected for 100s place) and 8 choices for the ones place (2 choices already chosen for 100s and 10s place)

No. of combinations = 2 x 9 x 8 = 144

Thanks for your solution. Will study it.

Hi Can anyone help with this question?

How many 3-digit number combinations are there on a 3-digit number lock if all the 3-digits used are different and the numbers are greater than 800?

Thanks.

livewith_vanilla:

super star:

please help me with this problem

Tank p with 40cm by 30cm base is filled with water till it reaches the height 55cm .water was then poured from tank p to tank q with base 100cmby20cm, untill the height of the water level in tank p became twice that of the water level in tank q.find the volume of water in tank q. give your ans in liters.

55x40x30=66000

40x30=1200
100x20=12000
12000+1200=13200
66000/13200=5
5x2=10
10x100x20=20000

20000cm3 = 20L

Ans:20L

others please double confirm answer.

You made a calculation error with \"100x20=12000\"
it should be 2000

so answer should be 30 litres

Amount of water you have in tank p which you want to pour into p and q in such a way that the height in p is twice q so let the height in q be 1 unit and the height in p be two units.

55x40x30=66000 (amt of water in p)

vol to be filled in p + vol to be filled in q = 66000 ml

40x30x2units +100x20x 1 unit = 66000 ml
2400 units + 2000 units = 66000 ml
4400 units = 66000 ml
1 unit = 15 cm
2000 x 15 = 30000ml = 30 litres

super star:

pls help me with this problem


fill in the blank
0.7:7/8=__ :___

Let me try:=
2 : 3 is also equal to 2 divide by 3

so 0.7 : 7/8
= 7/10 divide by 7/8
= 7/10 x 8/7
= 4/5
= 4 : 5

another way is to make to common denomintaors:
7/10 : 7/8
= 28/40 : 35/40
= 28 : 35
= 4 : 5

AM I correct?
THanks

you are right. so plus first tree so it should also be 21. pai say!

i also calculated 20. all the trees that were planted on mulitples of 5 and 10, in this case are the ones on 20m, 40m,… and 20 tress need not be removed.

ok. Thanks for taking time to clarify.

Oh another question, is it wrong to for example convert 4500m to km and write 4.500km? Is it mathematically wrong and will marks be deducted? Thanks.

Is the answer 77 or 78 1/3? Which is more acceptable? Thanks....... :?:


Apparently answer from schoolS' teacherS is 77. THanks.
Oh when I use 77 to workbacks, base and height don't tally.
When I use 78 1/3, they are ok.

Who that clever person who knows to change 94 to 90?

That was what I have been told to do. But I just want to know what should the answer be if it's 94. thanks, very stubborn me.

Ist of all which book are you talking about because you only mentioned ‘book’ method?


Not all books are reliable so have to be careful when using them.

Qn 1: In my opinion, in order to get the answer given by the ‘book’, the question should be phrased this way:-
What percentage of the pupils in the school are boys who go to school by car?

Qn 2: thewords used are not very clear. We could also interpret it as this year total of 13 units = 9600 cars and vans were sold? but number is not even divisible.

Qn 3: Your answer of 50% is correct. To calculate more than we have to use difference/boys x 100%. We cannot use 60 - 40 = 20 as final answer.

They are just my opinions.