The function Ro rounds a positive decimal number to its nearest intege

Question

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The function Ro rounds a positive decimal number to its nearest integer starting from its rightmost digit. What is the value of Ro(64.4ab5), where a and b are single digit positive integers?

(1) Ro(36.4a7) = 37
(2) Ro(87.b6) = 88

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sambitspm · Answer

See the attachment 
IMO A

yashikaaggarwal · Answer

IMO A

Statement 1: Ro(36.4a7) = 37
=> Rounding off to 37 means the tenth value after decimal is round off to upper digits(5,6,7,8,9) since 36.4a7 is given, nearest integer is 36.5
36.5 comes from the rounding off hundred to the nearest integer. That means 36.4(5,6,7,8,9)7
=> So value of a lies in (5,6,7,8,9)
Putting value of a in Ro(64.4ab5)
=> 64.4(5,6,7,8,9)b5
Well I think even if B is 0 to 9, A will be in range of 5 to 9 which is sufficient to round of 64.4(5,6,7,8,9) to 65
=> (sufficient)
Do correct where I am mistakening.

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HoneyLemon · Answer

C imo
The function Ro rounds a positive decimal number to its nearest integer starting from its rightmost digit. What is the value of Ro(64.4ab5), where a and b are single digit positive integers?
Ro(64.4ab5) ? We need to know the value of a and b .
(1) Ro(36.4a7) = 37

a can be = 4 or > 4 ,similarly b can be <4 or >4 .
if a = 4 , depending on b's value the round off value can change . Ro(64.4ab5) can be 64 or 65 .
if a >4 , then Ro(64.4ab5) = 65
Hence statement 1 is not sufficient .

(2) Ro(87.b6) = 88

b must be > = 4 .
if b = 4 , and a < 4 then Ro(64.4ab5) = 64
if b=4 and a >=4 then Ro(64.4ab5) = 65

Hence not sufficient .

Combining 1 and 2 .
Ro(36.4a7) = 37
Ro(87.b6) = 88
a and b at least 4 .
so Ro(64.4ab5) = 65 . Sufficient .

Hence C is my ans .

NKJJ1990 · Answer

The number is rounded off to the higher digit if the value is >= 5

Ro (64.4ab5) will be rounded off to Ro (64.4ac) where c = b+1

Statement 1 - Ro (36.4a7) = 37 
This says that a >= 4 
because:
- Assume a = 4,
36.447 -> 36.45 -> 36.5 -> 37
- However, if a = 3,
36.437 -> 36.44 -> 36.4 -> 36
- Now try this in 64.4ab5 -> 64.44c; we don't know the value of c here.
Statement I - insufficient

Statement 2 - Ro (87.b6) = 88
Again here b >=4
because:
- Assume b = 4,
87.46 -> 87.5 -> 88
- Assume b = 3
87.36 -> 87.4 -> 87
- Now try this in 64.4a45 -> 64.4a5 -> 64.4d (where d = a+1), but we don't know the value of a to determine the value of d.
Statement II - insufficient

Together:
a >= 4, b >=4
64.4ab5 -> 64.4445 -> 64.445 -> 64.45 -> 64.5 -> 65

Therefore, Answer C

exc4libur · Answer

(1) insufic

(36.4a7)=37
a>=4
a,b=4,1: (64.4ab5)=(64.4415)=64
a,b=5,1: (64.4ab5)=(64.4515)=65

(2) insufic

(87.b6)=88
b>=4
a,b=4,4: (64.4ab5)=(64.4445)=65
a,b=1,5: (64.4ab5)=(64.4155)=64

(1/2) sufic
a,b>=4,4: (64.4ab5)=(64.445)=65

Ans (C)

monikakumar · Answer

The function Ro rounds a positive decimal number to its nearest integer starting from its rightmost digit. What is the value of Ro(64.4ab5), where a and b are single digit positive integers?

(1) Ro(36.4a7) = 37
(2) Ro(87.b6) = 88

1) a can be 4 or greater than 4
insufficient, b value not known

2) b can be 4 or greater than 4 
insufficient, a value not known

1+2) b becomes 5 or greater than 5
so, a also becomes 5 or greater than 5
so sufficient

Ans C

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The function Ro rounds a positive decimal number to its nearest intege

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