Search found 50 matches

Thu Feb 08, 2018 1:35 am
Topic: BDMO 2017 National round Secondary 1
Replies: 11
Views: 549

Re: BDMO 2017 National round Secondary 1

The key to understanding this problem, as Ahmed pointed out, is that not all cases are equally likely to happen . The probabilities for the series to end in exactly 3 matches and to end in exactly 4 (or 5) matches are not equal, so the 20 cases listed above cannot be treated with equal weights. In g...
Wed Nov 01, 2017 7:15 pm
Forum: Secondary Level
Topic: AREA
Replies: 1
Views: 205

Re: AREA

Taking four pairs of sign for \$(x, y)\$ and considering magnitude of \$x\$ vs. that of \$y\$ in each of the four cases, you would get a square as the bounded region. It should then be a matter of moments to compute the area.
Tue Aug 22, 2017 10:04 pm
Forum: Algebra
Topic: Double inequality
Replies: 3
Views: 368

Re: Double inequality

There is a mistake in the variables of the problem. I've corrected \$ x, y, z\$ respectively to \$ a, b, c \$. We observe that \$ bc + ca + ab - 2abc \$ \$ = bc - abc + ca - abc + ab -abc + abc \$ \$ = bc(1-a) + ca(1-b) + ab(1-c) + abc \$ \$ = bc(b+c) + ca(c+a) + ab(a+b) + abc \geq 0 \$, because \$ a, b, c \$ eac...
Tue Feb 28, 2017 3:39 pm
Forum: Social Lounge
Topic: Probability-?
Replies: 2
Views: 414

Re: Probability-?

To make the correct probabilistic comparison, you'd need to know child mortality rates among 1-year child group and 2-year child group. If you want to compare baby boys only, you'd need to gather data for the boys, excluding the girls. A lower age doesn't necessarily correlate with a higher survival...
Tue Feb 07, 2017 4:32 pm
Topic: BDMO REGIONAL 2015
Replies: 5
Views: 805

Re: BDMO REGIONAL 2015

How did you find 14 number(s)? Did you rather mean 24? How can you find the sum 126 if you take one of the numbers to be 3?

Anyway, the phrase "the sum of any two among them" is ambiguous and does not seem to clarify what the question setters actually asked for.
Mon Feb 06, 2017 8:24 pm
Topic: BDMO NATIONAL JUNIOR 2012/03
Replies: 4
Views: 408

Re: BDMO NATIONAL JUNIOR 2012/03

One of the three cases will happen each day:
Rainy morning, Clear afternoon
Clear morning, Rainy afternoon
Clear morning, Clear afternoon

Right?

Can you now assign variable(s) to the no. of days in each case and relate the variables with 11, 16 and 13 in some equations?
Mon Jan 30, 2017 9:48 pm
Topic: Geometry
Replies: 10
Views: 870

Re: Geometry

No, it doesn't depend on anyone's personal consideration of diagonals. Sides are not diagonals, and diagonals are not lines. These two facts don't change with our opinions.
Mon Jan 30, 2017 9:30 pm
Topic: Geometry
Replies: 10
Views: 870

Re: Geometry

The way you are counting 1. views certain side(s) as diagonal(s). For example, if A and B are adjacent vertices, then AB is a side, not a diagonal. You might argue that no pair of the four points (A, B, C and D) is adjacent, but when you generalize the counting for 2013 sides by choosing any group o...
Sun Jan 22, 2017 6:47 pm
Topic: Geometry
Replies: 10
Views: 870

Re: Geometry

Why will any 4 points give 3 intersecting points of diagonals? Any group of 4 points will generate 2 unique diagonals, and the 2 diagonals will intersect at 1 point.
Mon Jan 09, 2017 4:04 pm
Forum: Physics
Topic: A problem of BdPhO'17
Replies: 5
Views: 1028

Re: A problem of BdPhO'17

Write the decay equation and apply the "law of conservation of momentum" to find the ratio. You may wish to apply "relativistic" momentum in your equation, depending on the level for which the problem has been devised.