SKILL TEST 2
Tick (✓) the correct answer:
1. Nitin was counting down from 31. Sumit was counting upwards
the numbers star
ting from 1 and he was calling out only the odd
numbers. What common number will they call out at the same
time if they were calling out at the same speed?
(a) 19
(b) 20
(c) 21
(d) 22
Answers
Given : Nitin was counting down from 31.
Sumit was counting upwards from 1 and was calling out only odd numbers
To Find : common number they call out at the same time
(a) 19
(b) 20
(c) 21
(d) 22
Solution:
1st called
31 and 1
Difference = 30
Now Nitin called = 31 - 1 = 30
and Sumit called = 1 + 2 = 3
Difference = 27
on 1st calling Difference = 30
on 2nd calling difference = 27
on 3rd calling difference = 24 and so on
0 = 30 + (n - 1)(-3)
=> n = 11
11th Calling
on 1st calling number was 31
31 + (11 - 1)(-1) = 31 - 10 = 21
on 11 th calling number = 21
or 1 + (11 - 1)*2 = 21
Hence common number called = 21 at same time
31 1
30 3
29 5
28 7
27 9
26 11
25 13
24 15
23 17
22 19
21 21
common number called = 21 at same time
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