Suppose N is an n-digit positive
integer such that
(a) all the n-digits are distinct; and
(b) the sum of any three consecutive
digits is divisible by 5.
Prove that n is at most 6. Further,
show that starting with any digit one
can find a six-digit number with these
properties.
i still search about a general and
complete solution about this
determine x in N where 7 divise 2^x +3^x
note = it is just an exercise in secondary
so dont go away...
maybe we must use separation of cases
methode....
A block is tied with a thread of length l
and moved in a horizontal circle on a
rough table. Coefficient of friction
between block and table is μ = 0.2.
Find tan θ, where θ is the angle
between acceleration and frictional
force at the instant when speed of
particle is v = (√(1.6lg))
Let A be a set of 16 positive integers
with the property that the product of
any two distinct numbers of A will
not exceed 1994. Show that there are
two numbers a and b in A which are
not relatively prime.
Let n be the number of ways in which
5 boys and 5 girls stand in a queue in
such a way that all the girls stand
consecutively in the queue. Let m be
the number of ways in which 5 boys
and 5 girls can stand in a queue in such
a way that exactly four girls stand
consecutively in the queue. Then the
value of (m/n) is
A heavy iron bar of weight W is having
its one end on the ground and the other
on the shoulder of a man. The rod
makes an angle θ with the horizontal.
What is the weight experienced by the
man?
Let n_1 < n_2 < n_3 < n_4 < n_5 be positive
integers such that n_1 + n_2 + n_3 + n_4 +
n_5 = 20. Then the number of such
distinct arrangements (n_1 , n_2 , n_3 , n_4 , n_5 )
is
The number of ways of distributing six
identical mathematics books and six
identical physics books among three
students such that each student gets
atleast one mathematics book and
atleast one physics book is ((5.5!)/k), then k
is
An eight digit number is formed from
1, 2, 3, 4 such that product of all digits
is always 3072, the total number of
ways is (23.^8 C_k ), where the value of k
is
There are 8 Hindi novels and 6 English
novels. 4 Hindi novels and 3 English
novels are selected and arranged in a
row such that they are alternate then
no. of ways is
In an xy plane the graph of the equation
(x−6)^2 +(y+5)^2 =16 is a circle. P(10,−5)
is on the circle. If PQ is a diameter of the
circle, what is the co-ordinate at Q?
Let a_n denote the number of all n-digit
positive integers formed by the digits
0, 1 or both such that no consecutive
digits in them are 0. Let b_n = the
number of such n-digit integers ending
with digit 1 and c_n = the number of
such n-digit integers ending with
digit 0.
1. Which of the following is correct?
(1) a_(17) = a_(16) + a_(15)
(2) c_(17) ≠ c_(16) + c_(15)
(3) b_(17) ≠ b_(16) + c_(16)
(4) a_(17) = c_(17) + b_(16)
2. The value of b_6 is
If a,b, and A of a triangle are
fixed and two possible values of the
third side be c_1 and c_2 such that
c_1 ^2 +c_1 c_2 +c_2 ^2 =a^2 , then find angle A.
x=^3 (√(7+5(√2)))+^3 (√(7−5(√2)))
1. According to a video, x=2
2. According to WolframAlpha,
x≈0.2071+0.3587i for “principal root”
and x=2(√2) for “real-valued root”
3. According to google, x≈2.8284
Please help and explain! :)
A wire of mass 9.8 × 10^(−3) kg per meter
passes over a frictionless pulley fixed
on the top of an inclined frictionless
plane which makes an angle of 30° with
the horizontal. Masses M_1 and M_2 are
tied at the two ends of the wire. The
mass M_1 rests on the plane and the
mass M_2 hangs freely vertically
downward. The whole system is in
equilibrium. Now a transverse wave
propagates along the wire with a
velocity of 100 m/s. Find M_1 and M_2
(g = 9.8 m/s^2 ).