Addition Problem

A B + C D = A A A AB+CD=AAA where A B AB and C D CD are two-digit numbers and A A A AAA is a three-digit number; A , B , C , A, B, C, and D D are distinct positive integers. In the addition problem above, what is the value of D D ?

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Cannot be determined 3 9 1

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3 solutions

AB + CD < 99 + 99 < 200 => AAA = 111
=> B+D = 1 or 11 =>
B + D = (3,8) (4,7) (5,6) (9,2) =>
So D cannot be determined

if A=1,B=8,C=9 and D=3 then AB+CD=AAA SO D=3

dibya ranjan - 6 years, 8 months ago

AAA is automatically 111, so A = 1 (B,C, & D)'s possible values are 2,3,4,5,6,7,8, & 9 here's what i found: AB + CD = AAA 18 + 93 = 111

so D is equal to 3!

Germene Begay - 6 years, 8 months ago

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THE ONLY POSSIBLE VALUE THAT GIVEN TO A IS 1, SO AB+CD=111 , FROM GIVEN OPTION D CAN TAKE EITHER 3 OR 9 .AND IF WE PUT D=9 IN THE ABOVE EQ. THEN WE CANN'T GET L.H.S =111 SO ONLY OPTION REMAINS FOR THE VALUE OF D IS 3.SO THE EQ, WILL BE 18+93=111 ...........................:)

hasnain abbas - 6 years, 6 months ago

18 + 93 = 111 ... so the answer could have been 3 .... But, in this case , B + CD = 8 + 93 = 101 (now, applying brute force, we get, D=3,4,5,6,7,8)

Sheikh Sakib Ishrak Shoumo - 6 years, 10 months ago

18+93=111,,as we know A=1is only possibility.. So taking A=1 and we need B+D=11 soB=8,D=3..@B+D=11. And C=4

Rohit Singh - 6 years, 10 months ago

why the answer cannot be determined? here the answer is D=3

dibya ranjan - 6 years, 8 months ago

B can not be 9, C already equals 9

عمرو إبراهيم - 6 years, 10 months ago

S i n c e t w o , 2 _ d i g i t n u m b e r s a d d t o t h i r d d i g i t , \displaystyle Since~two,~~2\_digit~~numbers~add~ to~third~digit, t h e t h i r d d i g i t m u s t b e o n l y 1. S o A = 1. \displaystyle ~the~third~digit~must~ be~only~~1.~~~~~~~~So~~A=1.

T h u s t h e s u m i s 111. W e s h o u l d g e t 1 a t u n i t p l a c e . \displaystyle Thus~the~sum~is~~111.~~We~should~get~ ~1~~at~unit~ place. T h a t i s B + D = 11 , w e c a n h a v e \displaystyle That~is~~B+D=11,~~we~can~have

8 + 3 = 11 O R 2 + 9 = 11. S o D c a n b e 3 O R 9. \displaystyle 8+3=11~~OR~~2+9=11.~~So~D~can~be~~3~OR~9. C a n n o t b e d e t e r m i n e d . \displaystyle~ Can~not~ be ~determined.

The equation should be B + C D = 101 B + CD = 101 instead of B + D = 11 B+D = 11 ?

You should further state explicit examples of different cases which yield a different value of D D . The reason is that just because something is (currently) possible, doesn't mean that it can actually occur.

FYI - To type equations in Latex, you just need to add \ ( \ ) (no spaces) around your math code.

Calvin Lin Staff - 6 years, 10 months ago

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We actually have B + C D = 101 B+CD=101 . The fact B + D = 11 B+D=11 follows from the fact that the unit digit of 111 111 is 1 1 and B , D B,D are the only digits responsible for it on the LHS. We have that B + D = 1 B+D=1 and B + D = 21 B+D=21 are impossible, thus B + D = 11 B+D=11 . This yields C = 9 C=9 , which means B + D = 11 , B , D 1 , 9 B+D=11, B,D\neq 1,9 is an equivalent problem to the one originally posted. Since it has multiple solutions, namely 6, so does the original problem.

mathh mathh - 6 years, 10 months ago

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Thanks for adding the explanation!

Calvin Lin Staff - 6 years, 10 months ago

Thank you for explaining my step very clearly.

Niranjan Khanderia - 6 years, 10 months ago

Thank you.

Niranjan Khanderia - 6 years, 10 months ago

To me with given details A ,B <c & D being distict positive nos,AAA will be 111 which can be by additions of AB =48 + CD= 63,can be 42 + 69 therefore D can be either 3 or 9..these are the options to choose.

K.K.GARG,India

Krishna Garg - 6 years, 10 months ago
Harri Bell-Thomas
Oct 11, 2014

The sum of 2 two digit numbers can't be greater than 198 (99+99), therefore;

A = 1

1B + CD = 111

So;

B + CD = 101

As the sum of 2 single-digit number can't be greater than 18,

C = 9

So;

B + 9D = 101

B + D = 11

Two unknowns can't be conclusively found from a single equation, meaning we don't have enough information to solve this problem.

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