On each of three pieces of paper a three digit number is written two of the digits are covered . The sum is 826. What is the sum of two covered digits?

9

Step-by-step explanation:

The diagram showing the three pieces of paper of three digit in which two of the letters were covered can be seen below.

From the diagram; we have;

243 , 1_7 , _26

Assuming the covered digits are _

The sum is 826.

i.e

243 + 1_7 + _26 = 826

The objective is to determine the sum of the two unknown digits

So; we need to think about what number can we add put in 1_7 to determine the covered digit in  _26

From ; 1_7 , we have the choice to pick from 0 - 9

Assuming the covered digit is 0; let's check if we are right

So; 243 + 107  +  _26 = 826

350 +   _26 = 826

_26 = 826 - 350

_26 = 476

So; the covered digit is in the position of 4 , but it doesn't tally together

i.e 426 is not the same as 476, which makes our assumption to be wrong.

Let consider the covered digit to be 5 for example.

So; 243 + 157  +  _26 = 826

400 +   _26 = 826

_26 = 826 - 400

_26 =  426

The covered digit is in the position of 4

SO;

426 = 426

Here , our assumption is right.

As such , the covered digits are 5 and 4

The sum of the two  covered digits are = 5 + 4 = 9

the answer is a) y= 2 csc [0.5 (x+pi/2)]-1

step-by-step explanation: