IPM mega final STD IV answer

on a play ground the number of bicycles are 5 times than the number of tricycles. if the total number of wheels are 39, then how many children in all were playing with their cycles?





Answers:
if the number of tricycle is y
then number of bicycle is 5y
so, 3y + 2 x 5y = 39
13y = 39
y = 3
bicycles = 5 x 3 = 15
total number of cycles = 3 + 15 = 18.

IPM mega finals STD IV answer

An electronic digital watch shows 20:07. What time should pass at the earliest after which the same digits apppear again in a different order?


checking the combinations in ascending order.
00.27
00.72
02.07
02.70
07.20
07:02

So, 00:27 is the time when all digits will reappear for the first time.
therefore, 00:27 - 20:07 = 4 hrs 20 mins will pass at the earliest.

Mega final Question STD IV answer

A student writes seven consecutive natural numbers and the sum of the smallest three number is 33, which of the following is the sum of the largest numbers?



Answer:

if the numbers are "a-1", "a", "a + 1". Then a = 33/3  = 11
so, the numbers are 10, 11, 12.
so the last three numbers are 14, 15, 16 
sum of 14, 15, 16 = 45

rationalization

7-time and work

Machine A and B produce 8000 clips in 4 hr and 6 hr respectively. They work alternately for 1 hour. Starting first with A, then 8000 chips will be produced in ..........................hours.

6-Time and work

A and B can do a job in 12 days. B and C can do the job in 16 days. After A has worked for 5 days and B has worked for 7 days, C can finish the rest in 13 days. In how many days can C do the work alone?

profit and loss

A sells a Car to B at a profit of 10%, B sells it to C at a profit of 20%. If C pays $ 2000, what did A pay for it?




Answer

Cost of Car to A = y

So, Buying price of B = 1.10y

Buying price of C = 1.10y x 1.2 = 2000

or, y = 2000 / (1.1x 1.2) = $ 1515.15

profit and loss

Two third of a consignment was sold at a profit of 6% and the rest at a loss of 3%. If however, there was an overall profit of Rs 540, the value of the consignement was ........................





Answer

Cost price of consignment = y

so, (2/3)y x 1.06 + (1/3)y x .97 = 540 + y

or, (2.12 + .97)y = 540 x 3 + 3y

or, 0.09y = 540 x 3 

or, y = 18000