Subtraction with Regrouping: 102 − 17

Subtraction with Regrouping Calculator
Minuend
Subtrahend

What is 102 − 17?

Answer

102 − 17 =
85

With regrouping across a zero: 2 borrows — there are no tens to borrow from, so 1 hundred becomes 10 tens, and 1 ten goes to the ones

102 − 17 in a column. Above the columns: the values after borrowing — a crossed-out digit is replaced by the number above it; +10 marks a column that received a borrowed ten.
09+10
1(was 1, now 0)0(was 0, now 9)2 (was 2, now 12)
−17
85

Column by column: 102 − 17

  • Ones: 2 is less than 7 — borrow 1 hundred across the zero: hundreds 1 → 0, tens 0 → 9; 12 − 7 = 5 — write 5.
  • Tens: after borrowing, 9; 9 − 1 = 8 — write 8.
  • Hundreds: after borrowing, 0 — a leading zero is not written.

102 − 17 = 85

Second check: 102 − 85 = 17

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Column subtractions of 17

ExampleDifference
75 − 1758
80 − 1763
82 − 1765
84 − 1767
86 − 1769
88 − 1771
91 − 1774
93 − 1776
95 − 1778
100 − 1783
102 − 1785
106 − 1789
109 − 1792
111 − 1794
115 − 1798
122 − 17105
153 − 17136
189 − 17172
200 − 17183
220 − 17203

FAQ

What is 102 − 17?

102 − 17 = 85

How do you check that 102 − 17 = 85?

Add the difference and the subtrahend: 85 + 17 = 102. Getting the minuend back means the difference is right.

How many times do you borrow in 102 − 17?

2 borrows: each time the top digit was smaller than the one below it, 1 was borrowed from the column on the left.

Why does 0 become 9 when borrowing in 102 − 17?

The zero has nothing to lend, so it first borrows 1 from its left neighbour and becomes 10; then it lends 1 to the column on its right and keeps 9.

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