*MEGATHREAD* - The 2014 entry BMAT Thread

Fred has a four-digit Personal Identification Number (PIN) for his card to draw money out of his
bank account. All possible 10 000 numbers are allowed. His bank has an unusual security
system: it requires customers to get exactly one digit wrong each time, and not to use the same
four-digit code as was used the previous time. Someone steals his card, but has no information
about Fred’s PIN.
How many numbers that the thief could try would be accepted as valid?

Strange question but if I understand it right, it is:
Three digits must be right so 1×1×1. But then another one must be wrong so from 10 possible digits, 9 can be used. However, he has used his card before and one of these numbers can't be used so only 8 are left. So 1×1×1×8 is 8 numbers.
Hope it is right...

Posted from TSR Mobile

no The answer is 35

Okay because it asks what the LARGEST number boys can be, you can assume that the 3 taking every subject are boys. Combine this information with the fact that 15 are doing chemistry means you have 12 people left. Of these 12, 9 are girls therefore they're only 3 boys left. Now we also know 13 are doing bio, 13 - 3 boys that are doing all subjects gives us 10 people doing bio. We only have 9 girls therefore one of the boys must be taking bio instead of maths or physics to make up the number ten. From this we can now say 3 boys are doing every subject + 2 boys are doing Maths, physics and Chem. Hope that helps

Could someone please explain 2013 Section 2 Q19 for me please:

Two resistors of R1 ohms and R2 ohms are connected in series to a battery which has an e.m.f of V.
Which formula gives the power dissipated by resistor R1?

Answer is (V^2 x R1)/(R1 + R2)^2

Thanks!

thank you !
Can you help me with this question please?
A railway station platform is 150 metres long. A train passing through the station is 100 metres
long including the locomotive. The front of the train passes one end of the platform at 10 o’clock
exactly and the rear of the train passes the other end of the platform 15 seconds later.
What is the speed of the train in kilometres per hour?

The answer is 60Km/h

I dont get the difference when they ask in S1, if something is necessary and sufficient
like for example here

“So far the only foolproof way of identifying a dinosaur’s sex has been to find unlaid eggsinside the body, and only two such fossils are known. Now a structure called medullary
bone, which is otherwise found only in the bones of female birds, has been identified inside
the femur of a 69 million-year-old T-Rex fossil. In birds the medullary bone is densely
mineralised and rich in blood vessels. It acts as a store of calcium and without it, the
calcium needed to form eggshells would have to come from the birds' normal bones,
leaving them vulnerable to osteoporosis. As their eggs form, the shell formation depletes
the medullary bone, which remains undetectable during brooding and until the next
ovulation.”
[Source: Jeff Hecht. New Scientist 11 June 2005. p 9]
If you are trying to determine that a dinosaur fossil is male, then the absence of any
detectable medullary bone in a complete skeleton would be:
A a necessary but not a sufficient condition;
B a sufficient but not a necessary condition;
C both a necessary and a sufficient condition;
D neither a necessary nor a sufficient condition.

I thought it would be B but its not?

You have to use the equation P=IV and V=IR. Substitute IR for V in the P=IV to give P=I^2 * R. To find I we can rearrange V=IR to give I=V/R. Now substitute what we know so V = emf V, and R is R1 + R2 therefore I=V/R1+R2. Now substitute this in the equation P=I^2 * R gives you (V^2*R)/(R1+R2)^2, seeing as we're calculating power from R1, the R in the top half the equation will be R1 giving you the answer.


The front of the train passes the start of the platform at 10:00. It then travels 150m so the front is at the end of the platform. For the end to be at the platform, it then has to travel another 100m (As this is the length of the train). From this we now know the front of the train travelled at total of 100+150=250m so the train travelled 0.25km in 15 seconds. 0.25/15 will gives us the speed, to make this easier to calculate you can convert into fractions so 1/4 * 1/15 to give 1/60 km/s. To convert this speed into km/h, you just times it by 60*60. 1/60 *60 = 1 km/min, 1*60 = 60 km/h.




Is the answer A? :P I'm not too good at these questions...but this is my understanding: necessary in this case means in order to determine that a dinosaur is male, the absence of medullary bone is required. Sufficient means that the absence of medullary bone is enough to say the dinosaur is male. Seeing as females may also have an absence of medullary bone when the shell formation depletes and males don't have one as they don't produce shells, it is possible then both males and females can have an absence of of medullary bone. Therefore an absence of medullary bone is not sufficient to determine sex but is a necessary finding to determine a male sex dinosaur.

yes youre right well done!BUT i thought everything that is necessary should be TRUE, so necessary in this case means in order to determine that a dinosaur is male, the absence of medullary bone is required. however it is not really "necessary"because it is possible then both males and females can have an absence of of medullary bone so we wouldnt be able to determine the gender of the dinosaur im just too confused wut

http://www.admissionstestingservice.org/images/20461-past-paper-2011-section-2-.pdf

Might be a simple question but can someone help me with q4?

To see if it's necessary you can completely forget about what the females have. The extract tells us ALL MALE dinosaurs will not have a medullary bone - an absence of medullary bone is a criteria, amongst others, that has to be met to determine male sex. An absence of medullary bone is 100% necessary in order for us to consider the dinosaur to be male. If there's a medullary bone then the dinosaur is 100% not male.
The information that tells us females and males can have an absence of medullary bone is used to see if it is sufficient.
Does this clear things up or have I confused you more? :P

Which of the following thermal decomposition reactions will require the highest
temperature?
A Ag2O → 2Ag + ½O2
B H2O2 → H2O + ½O2
C HgO → Hg + ½O2
D Na2O → 2Na + ½O2
E PbO2 → PbO + ½O2

can someone pls do this
A heart exerts a maximum (systolic) pressure of 152 mm Hg. This pressure is applied to an
aorta of cross sectional area 2.0 cm2.
What force must be generated by the heart in order to apply this pressure?
(Take 760 mm Hg to be 1.0 atmosphere which is 100 kPa.)
A 0.004 N
B 4 N
C 40 N
D 400 N
ans : B

sorry guys hehehe
Six friends went to their local agricultural show. They all decided to enter the ‘Guess the
Weight of the Bull’ competition. The guesses of the six friends are shown below in
hundredweight (cwt).
cwt
Wally 40
Herbert 37
Jack 26
Mary 19
Simon 9
Suzie 4
The average of their guesses was closer than any of their individual guesses. Suzie’s
guess is nearer than Wally’s.
What, to the nearest cwt, is the weight of the bull?
A 20
B 21
C 22
D 23
E 24

ANS : B