Explanation

Explanation

⇒  Let total examines is x.

⇒  65% of total examines has passed. 

⇒  student failed =100%−65%=35%

Then, 35% of examines have failed.

⇒  Number of failures is 420

∴  35% of x=420

∴   35x/100 = 420

 x=(420 * 100)/35

∴  x=1200

Thus, Total number of examines are 1200.

Explanation

The mean of 100 items is 30, so the total sum of all items is:

30 x 100 = 3000

However, two items were wrongly taken as 32 and 12 instead of 23 and 11, which means the correct total sum should be:

3000 - 32 - 12 + 23 + 11 = 2990

Since there are 100 items, the correct mean is:

2990 ÷ 100 = 29.9

So, the correct answer is: 29.9

Explanation

The formula #S_oo=a_1/(1-r)#

#a_1=-10# and #r=1/2#

#S_oo=-10/(1-1/2)#

#S_oo=-20#

Sh1-9-2023

Explanation

You can buy 2 envelopes only and have 1 cent left unless they are selling the envelope in parts,

in that case, you can buy 2*6/5=12/5=2.4

Sh1-9-2023

Explanation

400% of r = 4 * 100% of a 

                 =4 * a = 4a

   the percent of 400a with 4a 

         =4a/400a

         = 1/100

           1 %

sh1-9-2023

Explanation

Let  3x = 4y  = 5z =k

x = k/3 ,y =k/4 ,z =k/5

x : y : z = k/3 : k/4 : k/5

x : y : z =  20 :15 :12

Sh1-9-2023

Explanation

The biology and maths students be 6x and 7x 

now 6x = 90 

x = 90/6 

x = 15 

7x = 7 * 15 

7x = 105 

105 students are taking mants 

SH1-9-2023

Explanation

Sh1-9-2023

Explanation

Ratio of their salary = 9:4

Let salary of A = 9x

and of B = 4x

when salary of A increase we get,

Salary of A = 9x (1 + 15/100) = 5175

9x (115/100) = 5175

9x = 5175 * 100 / 115

9x = 4500

x = 500

So salary of B = 4x

4(500) = 2000

Therefore salary of B is Rs. 2000.

SH28-8-2023