Table:
0
A
B
C
D
E
1
State (class)
Vacator
Reason for change
Successor
Date of successors formal installation
2
Maryland (3)
Vacant
Sen. Thomas H. Hicks died during previous congress
John Creswell (UU)
March 9, 1865
3
New Jersey (2)
Vacant
Presented credentials as Sen-elect
John P. Stockton (D)
March 15, 1865
4
Tennessee (2)
Vacant
Tennessee re-admitted to the Union
Joseph S. Fowler (UU)
July 24, 1866
5
Tennessee (1)
Vacant
Tennessee re-admitted to the Union
David T. Patterson (U)
July 28, 1866
6
Vermont (3)
Jacob Collamer (R)
Died November 9, 1865
Luke P. Poland (R)
November 21, 1865
7
Vermont (1)
Solomon Foot (R)
Died March 28, 1866
George F. Edmunds (R)
April 3, 1866
8
New Jersey (1)
William Wright (D)
Died November 1, 1866
Frederick T. Frelinghuysen (R)
November 12, 1866
9
Nebraska (1)
New seat
Nebraska admitted to the Union March 1, 1867.
Thomas Tipton (R)
March 1, 1867

Questions and formulas:
Question: What change caused a change of staff in March 9, 1865?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,E1="March 9, 1865"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,E2:E9="March 9, 1865"),3))
Level: medium
Question: Who was the successor for the new seat?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,B1="New seat"),4))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,B2:B9="New seat"),4))
Level: medium
Question: What was the reason for change in staff in formal installations on March 15, 1865?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,E1="March 15, 1865"),3))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,E2:E9="March 15, 1865"),3))
Level: medium
Question: Who was the successor for the new seat?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,B1="New seat"),4))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,B2:B9="New seat"),4))
Level: medium