What is the value of 4 + 44 + 444 + 4444 + 44444?
- (a)49380
- (b)42300
- (c)41300
- (d)45000
Answer
Why
Correct — A. Add the terms one at a time and keep a running total.
4 + 44 = 48
48 + 444 = 492
492 + 4444 = 4936
4936 + 44444 = 49380 → option (a)
Check: every term is 4 times a string of 1s, so the sum is 4 × (1 + 11 + 111 + 1111 + 11111) = 4 × 12345 = 49380.
Why the others are wrong
- (b)42300 — It is below 48,888, which is 44444 + 4444, the two largest terms alone. A sum of five positive terms cannot be smaller than two of them added together.
- (c)41300 — It ends in 00, but the units column is five 4s = 20 and the tens column is four 4s plus the carried 2 = 18, so the total must end in 80.
- (d)45000 — A round figure that falls short: 44444 + 4444 already makes 48,888 before 4, 44 and 444 are added.
Concept
Each term is 4 times a repunit, a number written only with 1s: 44 = 4 × 11, 444 = 4 × 111, and so on.
The repunits 1 + 11 + 111 + 1111 + 11111 add to 12345. Their units column holds five 1s, the tens four, the hundreds three, the thousands two and the ten-thousands one, and no column carries.
So the whole sum is 4 × 12345 = 49380.
Column addition gives the same total, and the last two digits alone separate the options.
Units: five 4s = 20 → write 0, carry 2
Tens: four 4s + 2 = 18 → write 8, carry 1
Hundreds: three 4s + 1 = 13 → write 3, carry 1
Thousands: two 4s + 1 = 9, then ten-thousands: 4
Option (a) is the one choice ending in 80.
Key facts
- d + dd + ddd + … = d × (1 + 11 + 111 + …), so 4 + 44 + 444 + 4444 + 44444 = 4 × 12345.
- For up to nine terms, 1 + 11 + 111 + … writes the digits 1, 2, 3 … in order: 1 + 11 + 111 = 123.
- A total of positive terms is always larger than any part of it: here 44444 + 4444 = 48,888 is a floor.
Study next
Common traps
- Dropping the carry from the units column: the tens column is four 4s plus 2 = 18, and without the 2 it reads 16, turning the tens digit into 6.
- Choosing the nearest round option by estimate without checking a lower bound such as 44444 + 4444.
Here the sum is printed in full and the options sit thousands apart, so a floor from the two largest terms, or the last two digits, settles it before the full addition.
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